diff --git a/AK/URL.cpp b/AK/URL.cpp
index c613e4f12e5..4f1d96f0f0a 100644
--- a/AK/URL.cpp
+++ b/AK/URL.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/LexicalPath.h>
 #include <AK/StringBuilder.h>
@@ -14,26 +15,6 @@
 
 namespace AK {
 
-constexpr bool is_ascii_alpha(u32 code_point)
-{
-    return ('a' <= code_point && code_point <= 'z') || ('A' <= code_point && code_point <= 'Z');
-}
-
-constexpr bool is_ascii_digit(u32 code_point)
-{
-    return '0' <= code_point && code_point <= '9';
-}
-
-constexpr bool is_ascii_alphanumeric(u32 code_point)
-{
-    return is_ascii_alpha(code_point) || is_ascii_digit(code_point);
-}
-
-constexpr bool is_ascii_hex_digit(u32 code_point)
-{
-    return is_ascii_digit(code_point) || (code_point >= 'a' && code_point <= 'f') || (code_point >= 'A' && code_point <= 'F');
-}
-
 // FIXME: It could make sense to force users of URL to use URLParser::parse() explicitly instead of using a constructor.
 URL::URL(StringView const& string)
     : URL(URLParser::parse({}, string))
@@ -403,17 +384,6 @@ String URL::percent_encode(StringView const& input, URL::PercentEncodeSet set)
     return builder.to_string();
 }
 
-constexpr u8 parse_hex_digit(u8 digit)
-{
-    if (digit >= '0' && digit <= '9')
-        return digit - '0';
-    if (digit >= 'a' && digit <= 'f')
-        return digit - 'a' + 10;
-    if (digit >= 'A' && digit <= 'F')
-        return digit - 'A' + 10;
-    VERIFY_NOT_REACHED();
-}
-
 String URL::percent_decode(StringView const& input)
 {
     if (!input.contains('%'))
@@ -427,9 +397,9 @@ String URL::percent_decode(StringView const& input)
             builder.append_code_point(*it);
         } else {
             ++it;
-            u8 byte = parse_hex_digit(*it) << 4;
+            u8 byte = parse_ascii_hex_digit(*it) << 4;
             ++it;
-            byte += parse_hex_digit(*it);
+            byte += parse_ascii_hex_digit(*it);
             builder.append(byte);
         }
     }
diff --git a/AK/URLParser.cpp b/AK/URLParser.cpp
index 4318bf5dc78..ad74dd3f3d1 100644
--- a/AK/URLParser.cpp
+++ b/AK/URLParser.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/Optional.h>
 #include <AK/SourceLocation.h>
@@ -15,26 +16,6 @@
 
 namespace AK {
 
-constexpr bool is_ascii_alpha(u32 code_point)
-{
-    return ('a' <= code_point && code_point <= 'z') || ('A' <= code_point && code_point <= 'Z');
-}
-
-constexpr bool is_ascii_digit(u32 code_point)
-{
-    return '0' <= code_point && code_point <= '9';
-}
-
-constexpr bool is_ascii_alphanumeric(u32 code_point)
-{
-    return is_ascii_alpha(code_point) || is_ascii_digit(code_point);
-}
-
-constexpr bool is_ascii_hex_digit(u32 code_point)
-{
-    return is_ascii_digit(code_point) || (code_point >= 'a' && code_point <= 'f') || (code_point >= 'A' && code_point <= 'F');
-}
-
 constexpr bool is_url_code_point(u32 code_point)
 {
     // FIXME: [...] and code points in the range U+00A0 to U+10FFFD, inclusive, excluding surrogates and noncharacters.
diff --git a/Userland/Libraries/LibGUI/EditingEngine.cpp b/Userland/Libraries/LibGUI/EditingEngine.cpp
index 2d02293ba94..99f2f779be1 100644
--- a/Userland/Libraries/LibGUI/EditingEngine.cpp
+++ b/Userland/Libraries/LibGUI/EditingEngine.cpp
@@ -4,12 +4,23 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <LibGUI/EditingEngine.h>
 #include <LibGUI/Event.h>
 #include <LibGUI/TextEditor.h>
 
 namespace GUI {
 
+constexpr bool is_vim_alphanumeric(u32 code_point)
+{
+    return is_ascii_alphanumeric(code_point) || code_point == '_';
+}
+
+constexpr bool is_vim_punctuation(u32 code_point)
+{
+    return is_ascii_punctuation(code_point) && code_point != '_';
+}
+
 EditingEngine::~EditingEngine()
 {
 }
@@ -379,15 +390,7 @@ TextPosition EditingEngine::find_beginning_of_next_word()
      * If the end of the input is reached, jump there
      */
 
-    auto vim_isalnum = [](int c) {
-        return c == '_' || isalnum(c);
-    };
-
-    auto vim_ispunct = [](int c) {
-        return c != '_' && ispunct(c);
-    };
-
-    bool started_on_punct = vim_ispunct(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
+    bool started_on_punct = is_vim_punctuation(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
     bool has_seen_whitespace = false;
     bool is_first_line = true;
     auto& lines = m_editor->lines();
@@ -409,18 +412,18 @@ TextPosition EditingEngine::find_beginning_of_next_word()
             const u32* line_chars = line.view().code_points();
             const u32 current_char = line_chars[column_index];
 
-            if (started_on_punct && vim_isalnum(current_char)) {
+            if (started_on_punct && is_vim_alphanumeric(current_char)) {
                 return { line_index, column_index };
             }
 
-            if (vim_ispunct(current_char) && !started_on_punct) {
+            if (is_vim_punctuation(current_char) && !started_on_punct) {
                 return { line_index, column_index };
             }
 
-            if (isspace(current_char))
+            if (is_ascii_space(current_char))
                 has_seen_whitespace = true;
 
-            if (has_seen_whitespace && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
+            if (has_seen_whitespace && (is_vim_alphanumeric(current_char) || is_vim_punctuation(current_char))) {
                 return { line_index, column_index };
             }
 
@@ -449,14 +452,6 @@ TextPosition EditingEngine::find_end_of_next_word()
      * If the end of the input is reached, jump there
      */
 
-    auto vim_isalnum = [](int c) {
-        return c == '_' || isalnum(c);
-    };
-
-    auto vim_ispunct = [](int c) {
-        return c != '_' && ispunct(c);
-    };
-
     bool is_first_line = true;
     bool is_first_iteration = true;
     auto& lines = m_editor->lines();
@@ -481,7 +476,7 @@ TextPosition EditingEngine::find_end_of_next_word()
             const u32* line_chars = line.view().code_points();
             const u32 current_char = line_chars[column_index];
 
-            if (column_index == lines.at(line_index).length() - 1 && !is_first_iteration && (vim_isalnum(current_char) || vim_ispunct(current_char)))
+            if (column_index == lines.at(line_index).length() - 1 && !is_first_iteration && (is_vim_alphanumeric(current_char) || is_vim_punctuation(current_char)))
                 return { line_index, column_index };
             else if (column_index == lines.at(line_index).length() - 1) {
                 is_first_iteration = false;
@@ -490,10 +485,10 @@ TextPosition EditingEngine::find_end_of_next_word()
 
             const u32 next_char = line_chars[column_index + 1];
 
-            if (!is_first_iteration && vim_isalnum(current_char) && (isspace(next_char) || vim_ispunct(next_char)))
+            if (!is_first_iteration && is_vim_alphanumeric(current_char) && (is_ascii_space(next_char) || is_vim_punctuation(next_char)))
                 return { line_index, column_index };
 
-            if (!is_first_iteration && vim_ispunct(current_char) && (isspace(next_char) || vim_isalnum(next_char)))
+            if (!is_first_iteration && is_vim_punctuation(current_char) && (is_ascii_space(next_char) || is_vim_alphanumeric(next_char)))
                 return { line_index, column_index };
 
             if (line_index == lines.size() - 1 && column_index == line.length() - 1) {
@@ -513,15 +508,7 @@ void EditingEngine::move_to_end_of_next_word()
 
 TextPosition EditingEngine::find_end_of_previous_word()
 {
-    auto vim_isalnum = [](int c) {
-        return c == '_' || isalnum(c);
-    };
-
-    auto vim_ispunct = [](int c) {
-        return c != '_' && ispunct(c);
-    };
-
-    bool started_on_punct = vim_ispunct(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
+    bool started_on_punct = is_vim_punctuation(m_editor->current_line().to_utf8().characters()[m_editor->cursor().column()]);
     bool is_first_line = true;
     bool has_seen_whitespace = false;
     auto& lines = m_editor->lines();
@@ -545,19 +532,19 @@ TextPosition EditingEngine::find_end_of_previous_word()
             const u32* line_chars = line.view().code_points();
             const u32 current_char = line_chars[column_index];
 
-            if (started_on_punct && vim_isalnum(current_char)) {
+            if (started_on_punct && is_vim_alphanumeric(current_char)) {
                 return { line_index, column_index };
             }
 
-            if (vim_ispunct(current_char) && !started_on_punct) {
+            if (is_vim_punctuation(current_char) && !started_on_punct) {
                 return { line_index, column_index };
             }
 
-            if (isspace(current_char)) {
+            if (is_ascii_space(current_char)) {
                 has_seen_whitespace = true;
             }
 
-            if (has_seen_whitespace && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
+            if (has_seen_whitespace && (is_vim_alphanumeric(current_char) || is_vim_punctuation(current_char))) {
                 return { line_index, column_index };
             }
 
@@ -580,14 +567,6 @@ void EditingEngine::move_to_end_of_previous_word()
 
 TextPosition EditingEngine::find_beginning_of_previous_word()
 {
-    auto vim_isalnum = [](int c) {
-        return c == '_' || isalnum(c);
-    };
-
-    auto vim_ispunct = [](int c) {
-        return c != '_' && ispunct(c);
-    };
-
     bool is_first_iterated_line = true;
     bool is_first_iteration = true;
     auto& lines = m_editor->lines();
@@ -618,7 +597,7 @@ TextPosition EditingEngine::find_beginning_of_previous_word()
             const u32* line_chars = line.view().code_points();
             const u32 current_char = line_chars[column_index];
 
-            if (column_index == 0 && !is_first_iteration && (vim_isalnum(current_char) || vim_ispunct(current_char))) {
+            if (column_index == 0 && !is_first_iteration && (is_vim_alphanumeric(current_char) || is_vim_punctuation(current_char))) {
                 return { line_index, column_index };
             } else if (line_index == 0 && column_index == 0) {
                 return { line_index, column_index };
@@ -629,10 +608,10 @@ TextPosition EditingEngine::find_beginning_of_previous_word()
 
             const u32 next_char = line_chars[column_index - 1];
 
-            if (!is_first_iteration && vim_isalnum(current_char) && (isspace(next_char) || vim_ispunct(next_char)))
+            if (!is_first_iteration && is_vim_alphanumeric(current_char) && (is_ascii_space(next_char) || is_vim_punctuation(next_char)))
                 return { line_index, column_index };
 
-            if (!is_first_iteration && vim_ispunct(current_char) && (isspace(next_char) || vim_isalnum(next_char)))
+            if (!is_first_iteration && is_vim_punctuation(current_char) && (is_ascii_space(next_char) || is_vim_alphanumeric(next_char)))
                 return { line_index, column_index };
 
             is_first_iteration = false;
diff --git a/Userland/Libraries/LibGUI/TextDocument.cpp b/Userland/Libraries/LibGUI/TextDocument.cpp
index faa647dda89..93ba964fc9d 100644
--- a/Userland/Libraries/LibGUI/TextDocument.cpp
+++ b/Userland/Libraries/LibGUI/TextDocument.cpp
@@ -5,6 +5,7 @@
  */
 
 #include <AK/Badge.h>
+#include <AK/CharacterTypes.h>
 #include <AK/ScopeGuard.h>
 #include <AK/StringBuilder.h>
 #include <AK/Utf8View.h>
@@ -12,7 +13,6 @@
 #include <LibGUI/TextDocument.h>
 #include <LibGUI/TextEditor.h>
 #include <LibRegex/Regex.h>
-#include <ctype.h>
 
 namespace GUI {
 
@@ -104,7 +104,7 @@ size_t TextDocumentLine::first_non_whitespace_column() const
 {
     for (size_t i = 0; i < length(); ++i) {
         auto code_point = code_points()[i];
-        if (!isspace(code_point))
+        if (!is_ascii_space(code_point))
             return i;
     }
     return length();
@@ -114,7 +114,7 @@ Optional<size_t> TextDocumentLine::last_non_whitespace_column() const
 {
     for (ssize_t i = length() - 1; i >= 0; --i) {
         auto code_point = code_points()[i];
-        if (!isspace(code_point))
+        if (!is_ascii_space(code_point))
             return i;
     }
     return {};
@@ -124,7 +124,7 @@ bool TextDocumentLine::ends_in_whitespace() const
 {
     if (!length())
         return false;
-    return isspace(code_points()[length() - 1]);
+    return is_ascii_space(code_points()[length() - 1]);
 }
 
 bool TextDocumentLine::can_select() const
@@ -638,11 +638,11 @@ TextPosition TextDocument::first_word_break_before(const TextPosition& position,
     if (target.column() == line.length())
         modifier = 1;
 
-    auto is_start_alphanumeric = isalnum(line.code_points()[target.column() - modifier]);
+    auto is_start_alphanumeric = is_ascii_alphanumeric(line.code_points()[target.column() - modifier]);
 
     while (target.column() > 0) {
         auto prev_code_point = line.code_points()[target.column() - 1];
-        if ((is_start_alphanumeric && !isalnum(prev_code_point)) || (!is_start_alphanumeric && isalnum(prev_code_point)))
+        if ((is_start_alphanumeric && !is_ascii_alphanumeric(prev_code_point)) || (!is_start_alphanumeric && is_ascii_alphanumeric(prev_code_point)))
             break;
         target.set_column(target.column() - 1);
     }
@@ -662,11 +662,11 @@ TextPosition TextDocument::first_word_break_after(const TextPosition& position)
         return TextPosition(position.line() + 1, 0);
     }
 
-    auto is_start_alphanumeric = isalnum(line.code_points()[target.column()]);
+    auto is_start_alphanumeric = is_ascii_alphanumeric(line.code_points()[target.column()]);
 
     while (target.column() < line.length()) {
         auto next_code_point = line.code_points()[target.column()];
-        if ((is_start_alphanumeric && !isalnum(next_code_point)) || (!is_start_alphanumeric && isalnum(next_code_point)))
+        if ((is_start_alphanumeric && !is_ascii_alphanumeric(next_code_point)) || (!is_start_alphanumeric && is_ascii_alphanumeric(next_code_point)))
             break;
         target.set_column(target.column() + 1);
     }
diff --git a/Userland/Libraries/LibGUI/TextEditor.cpp b/Userland/Libraries/LibGUI/TextEditor.cpp
index 13d98504faa..a1299aee928 100644
--- a/Userland/Libraries/LibGUI/TextEditor.cpp
+++ b/Userland/Libraries/LibGUI/TextEditor.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/ScopeGuard.h>
 #include <AK/StringBuilder.h>
@@ -25,7 +26,6 @@
 #include <LibGfx/FontDatabase.h>
 #include <LibGfx/Palette.h>
 #include <LibSyntax/Highlighter.h>
-#include <ctype.h>
 #include <fcntl.h>
 #include <math.h>
 #include <stdio.h>
@@ -1232,12 +1232,12 @@ size_t TextEditor::number_of_selected_words() const
     bool in_word = false;
     auto selected_text = this->selected_text();
     for (char c : selected_text) {
-        if (in_word && isspace(c)) {
+        if (in_word && is_ascii_space(c)) {
             in_word = false;
             word_count++;
             continue;
         }
-        if (!in_word && !isspace(c))
+        if (!in_word && !is_ascii_space(c))
             in_word = true;
     }
     if (in_word)
@@ -1561,7 +1561,7 @@ void TextEditor::recompute_visual_lines(size_t line_index)
         auto glyph_spacing = font().glyph_spacing();
         for (size_t i = 0; i < line.length(); ++i) {
             auto code_point = line.code_points()[i];
-            if (isspace(code_point)) {
+            if (is_ascii_space(code_point)) {
                 last_whitespace_index = i;
                 line_width_since_last_whitespace = 0;
             }
diff --git a/Userland/Libraries/LibJS/Runtime/GlobalObject.cpp b/Userland/Libraries/LibJS/Runtime/GlobalObject.cpp
index 7d9d92b498c..a38489aae5b 100644
--- a/Userland/Libraries/LibJS/Runtime/GlobalObject.cpp
+++ b/Userland/Libraries/LibJS/Runtime/GlobalObject.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Hex.h>
 #include <AK/Platform.h>
 #include <AK/TemporaryChange.h>
@@ -56,7 +57,6 @@
 #include <LibJS/Runtime/TypedArrayConstructor.h>
 #include <LibJS/Runtime/TypedArrayPrototype.h>
 #include <LibJS/Runtime/Value.h>
-#include <ctype.h>
 
 namespace JS {
 
@@ -249,16 +249,10 @@ JS_DEFINE_NATIVE_FUNCTION(GlobalObject::parse_int)
     }
 
     auto parse_digit = [&](u32 code_point, i32 radix) -> Optional<i32> {
-        i32 digit = -1;
-
-        if (isdigit(code_point))
-            digit = code_point - '0';
-        else if (islower(code_point))
-            digit = 10 + (code_point - 'a');
-        else if (isupper(code_point))
-            digit = 10 + (code_point - 'A');
-
-        if (digit == -1 || digit >= radix)
+        if (!is_ascii_hex_digit(code_point) || radix <= 0)
+            return {};
+        auto digit = parse_ascii_hex_digit(code_point);
+        if (digit >= (u32)radix)
             return {};
         return digit;
     };
diff --git a/Userland/Libraries/LibLine/Editor.cpp b/Userland/Libraries/LibLine/Editor.cpp
index 1bdcc4040bd..d6d57ac9112 100644
--- a/Userland/Libraries/LibLine/Editor.cpp
+++ b/Userland/Libraries/LibLine/Editor.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "Editor.h"
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/GenericLexer.h>
 #include <AK/JsonObject.h>
@@ -19,7 +20,6 @@
 #include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
 #include <LibCore/Notifier.h>
-#include <ctype.h>
 #include <errno.h>
 #include <signal.h>
 #include <stdio.h>
@@ -1338,7 +1338,7 @@ void Editor::refresh_display()
     auto print_character_at = [this](size_t i) {
         StringBuilder builder;
         auto c = m_buffer[i];
-        bool should_print_masked = isascii(c) && iscntrl(c) && c != '\n';
+        bool should_print_masked = is_ascii_control(c) && c != '\n';
         bool should_print_caret = c < 64 && should_print_masked;
         if (should_print_caret)
             builder.appendff("^{:c}", c + 64);
@@ -1722,7 +1722,7 @@ Editor::VTState Editor::actual_rendered_string_length_step(StringMetrics& metric
             current_line.length = 0;
             return state;
         }
-        if (isascii(c) && iscntrl(c) && c != '\n')
+        if (is_ascii_control(c) && c != '\n')
             current_line.masked_chars.append({ index, 1, c < 64 ? 2u : 4u }); // if the character cannot be represented as ^c, represent it as \xbb.
         // FIXME: This will not support anything sophisticated
         ++current_line.length;
@@ -1740,7 +1740,7 @@ Editor::VTState Editor::actual_rendered_string_length_step(StringMetrics& metric
         // FIXME: This does not support non-VT (aside from set-title) escapes
         return state;
     case Bracket:
-        if (isdigit(c)) {
+        if (is_ascii_digit(c)) {
             return BracketArgsSemi;
         }
         return state;
@@ -1748,7 +1748,7 @@ Editor::VTState Editor::actual_rendered_string_length_step(StringMetrics& metric
         if (c == ';') {
             return Bracket;
         }
-        if (!isdigit(c))
+        if (!is_ascii_digit(c))
             state = Free;
         return state;
     case Title:
@@ -1848,7 +1848,7 @@ Vector<size_t, 2> Editor::vt_dsr()
             m_incomplete_data.append(c);
             continue;
         case SawBracket:
-            if (isdigit(c)) {
+            if (is_ascii_digit(c)) {
                 state = InFirstCoordinate;
                 coordinate_buffer.append(c);
                 continue;
@@ -1856,7 +1856,7 @@ Vector<size_t, 2> Editor::vt_dsr()
             m_incomplete_data.append(c);
             continue;
         case InFirstCoordinate:
-            if (isdigit(c)) {
+            if (is_ascii_digit(c)) {
                 coordinate_buffer.append(c);
                 continue;
             }
@@ -1872,7 +1872,7 @@ Vector<size_t, 2> Editor::vt_dsr()
             m_incomplete_data.append(c);
             continue;
         case SawSemicolon:
-            if (isdigit(c)) {
+            if (is_ascii_digit(c)) {
                 state = InSecondCoordinate;
                 coordinate_buffer.append(c);
                 continue;
@@ -1880,7 +1880,7 @@ Vector<size_t, 2> Editor::vt_dsr()
             m_incomplete_data.append(c);
             continue;
         case InSecondCoordinate:
-            if (isdigit(c)) {
+            if (is_ascii_digit(c)) {
                 coordinate_buffer.append(c);
                 continue;
             }
diff --git a/Userland/Libraries/LibLine/InternalFunctions.cpp b/Userland/Libraries/LibLine/InternalFunctions.cpp
index a5a45f14dd9..b94f8d40679 100644
--- a/Userland/Libraries/LibLine/InternalFunctions.cpp
+++ b/Userland/Libraries/LibLine/InternalFunctions.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/FileStream.h>
 #include <AK/ScopeGuard.h>
 #include <AK/ScopedValueRollback.h>
@@ -11,7 +12,6 @@
 #include <AK/TemporaryChange.h>
 #include <LibCore/File.h>
 #include <LibLine/Editor.h>
-#include <ctype.h>
 #include <stdio.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -84,7 +84,7 @@ void Editor::cursor_left_word()
         for (;;) {
             if (m_cursor == 0)
                 break;
-            if (skipped_at_least_one_character && !isalnum(m_buffer[m_cursor - 1])) // stop *after* a non-alnum, but only if it changes the position
+            if (skipped_at_least_one_character && !is_ascii_alphanumeric(m_buffer[m_cursor - 1])) // stop *after* a non-alnum, but only if it changes the position
                 break;
             skipped_at_least_one_character = true;
             --m_cursor;
@@ -109,7 +109,7 @@ void Editor::cursor_right_word()
         for (;;) {
             if (m_cursor >= m_buffer.size())
                 break;
-            if (!isalnum(m_buffer[++m_cursor]))
+            if (!is_ascii_alphanumeric(m_buffer[++m_cursor]))
                 break;
         }
         m_buffer.take_last();
@@ -178,7 +178,7 @@ void Editor::erase_word_backwards()
     // A word here is space-separated. `foo=bar baz` is two words.
     bool has_seen_nonspace = false;
     while (m_cursor > 0) {
-        if (isspace(m_buffer[m_cursor - 1])) {
+        if (is_ascii_space(m_buffer[m_cursor - 1])) {
             if (has_seen_nonspace)
                 break;
         } else {
@@ -375,27 +375,27 @@ void Editor::transpose_words()
 
     // Move to end of word under (or after) caret.
     size_t cursor = m_cursor;
-    while (cursor < m_buffer.size() && !isalnum(m_buffer[cursor]))
+    while (cursor < m_buffer.size() && !is_ascii_alphanumeric(m_buffer[cursor]))
         ++cursor;
-    while (cursor < m_buffer.size() && isalnum(m_buffer[cursor]))
+    while (cursor < m_buffer.size() && is_ascii_alphanumeric(m_buffer[cursor]))
         ++cursor;
 
     // Move left over second word and the space to its right.
     size_t end = cursor;
     size_t start = cursor;
-    while (start > 0 && !isalnum(m_buffer[start - 1]))
+    while (start > 0 && !is_ascii_alphanumeric(m_buffer[start - 1]))
         --start;
-    while (start > 0 && isalnum(m_buffer[start - 1]))
+    while (start > 0 && is_ascii_alphanumeric(m_buffer[start - 1]))
         --start;
     size_t start_second_word = start;
 
     // Move left over space between the two words.
-    while (start > 0 && !isalnum(m_buffer[start - 1]))
+    while (start > 0 && !is_ascii_alphanumeric(m_buffer[start - 1]))
         --start;
     size_t start_gap = start;
 
     // Move left over first word.
-    while (start > 0 && isalnum(m_buffer[start - 1]))
+    while (start > 0 && is_ascii_alphanumeric(m_buffer[start - 1]))
         --start;
 
     if (start != start_gap) {
@@ -452,7 +452,7 @@ void Editor::erase_alnum_word_backwards()
     // A word here is contiguous alnums. `foo=bar baz` is three words.
     bool has_seen_alnum = false;
     while (m_cursor > 0) {
-        if (!isalnum(m_buffer[m_cursor - 1])) {
+        if (!is_ascii_alphanumeric(m_buffer[m_cursor - 1])) {
             if (has_seen_alnum)
                 break;
         } else {
@@ -467,7 +467,7 @@ void Editor::erase_alnum_word_forwards()
     // A word here is contiguous alnums. `foo=bar baz` is three words.
     bool has_seen_alnum = false;
     while (m_cursor < m_buffer.size()) {
-        if (!isalnum(m_buffer[m_cursor])) {
+        if (!is_ascii_alphanumeric(m_buffer[m_cursor])) {
             if (has_seen_alnum)
                 break;
         } else {
@@ -480,15 +480,15 @@ void Editor::erase_alnum_word_forwards()
 void Editor::case_change_word(Editor::CaseChangeOp change_op)
 {
     // A word here is contiguous alnums. `foo=bar baz` is three words.
-    while (m_cursor < m_buffer.size() && !isalnum(m_buffer[m_cursor]))
+    while (m_cursor < m_buffer.size() && !is_ascii_alphanumeric(m_buffer[m_cursor]))
         ++m_cursor;
     size_t start = m_cursor;
-    while (m_cursor < m_buffer.size() && isalnum(m_buffer[m_cursor])) {
+    while (m_cursor < m_buffer.size() && is_ascii_alphanumeric(m_buffer[m_cursor])) {
         if (change_op == CaseChangeOp::Uppercase || (change_op == CaseChangeOp::Capital && m_cursor == start)) {
-            m_buffer[m_cursor] = toupper(m_buffer[m_cursor]);
+            m_buffer[m_cursor] = to_ascii_uppercase(m_buffer[m_cursor]);
         } else {
             VERIFY(change_op == CaseChangeOp::Lowercase || (change_op == CaseChangeOp::Capital && m_cursor > start));
-            m_buffer[m_cursor] = tolower(m_buffer[m_cursor]);
+            m_buffer[m_cursor] = to_ascii_lowercase(m_buffer[m_cursor]);
         }
         ++m_cursor;
         m_refresh_needed = true;
diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index 68009575e07..d508851ab07 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -7,10 +7,9 @@
 #include "RegexByteCode.h"
 #include "AK/StringBuilder.h"
 #include "RegexDebug.h"
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 
-#include <ctype.h>
-
 namespace regex {
 
 const char* OpCode::name(OpCodeId opcode_id)
@@ -241,7 +240,7 @@ ALWAYS_INLINE ExecutionResult OpCode_CheckBegin::execute(const MatchInput& input
 
 ALWAYS_INLINE ExecutionResult OpCode_CheckBoundary::execute(const MatchInput& input, MatchState& state, MatchOutput&) const
 {
-    auto isword = [](auto ch) { return isalnum(ch) || ch == '_'; };
+    auto isword = [](auto ch) { return is_ascii_alphanumeric(ch) || ch == '_'; };
     auto is_word_boundary = [&] {
         if (state.string_position == input.view.length()) {
             if (state.string_position > 0 && isword(input.view[state.string_position - 1]))
@@ -510,8 +509,8 @@ ALWAYS_INLINE void OpCode_Compare::compare_char(const MatchInput& input, MatchSt
     u32 ch2 = input.view[state.string_position];
 
     if (input.regex_options & AllFlags::Insensitive) {
-        ch1 = tolower(ch1);
-        ch2 = tolower(ch2);
+        ch1 = to_ascii_lowercase(ch1);
+        ch2 = to_ascii_uppercase(ch2);
     }
 
     if (ch1 == ch2) {
@@ -551,7 +550,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
 {
     switch (character_class) {
     case CharClass::Alnum:
-        if (isalnum(ch)) {
+        if (is_ascii_alphanumeric(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -559,11 +558,11 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Alpha:
-        if (isalpha(ch))
+        if (is_ascii_alpha(ch))
             ++state.string_position;
         break;
     case CharClass::Blank:
-        if (ch == ' ' || ch == '\t') {
+        if (is_ascii_blank(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -571,7 +570,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Cntrl:
-        if (iscntrl(ch)) {
+        if (is_ascii_control(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -579,7 +578,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Digit:
-        if (isdigit(ch)) {
+        if (is_ascii_digit(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -587,7 +586,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Graph:
-        if (isgraph(ch)) {
+        if (is_ascii_graphical(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -595,7 +594,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Lower:
-        if (islower(ch) || ((input.regex_options & AllFlags::Insensitive) && isupper(ch))) {
+        if (is_ascii_lower_alpha(ch) || ((input.regex_options & AllFlags::Insensitive) && is_ascii_upper_alpha(ch))) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -603,7 +602,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Print:
-        if (isprint(ch)) {
+        if (is_ascii_printable(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -611,7 +610,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Punct:
-        if (ispunct(ch)) {
+        if (is_ascii_punctuation(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -619,7 +618,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Space:
-        if (isspace(ch)) {
+        if (is_ascii_space(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -627,7 +626,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Upper:
-        if (isupper(ch) || ((input.regex_options & AllFlags::Insensitive) && islower(ch))) {
+        if (is_ascii_upper_alpha(ch) || ((input.regex_options & AllFlags::Insensitive) && is_ascii_lower_alpha(ch))) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -635,7 +634,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Word:
-        if (isalnum(ch) || ch == '_') {
+        if (is_ascii_alphanumeric(ch) || ch == '_') {
             if (inverse)
                 inverse_matched = true;
             else
@@ -643,7 +642,7 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
         }
         break;
     case CharClass::Xdigit:
-        if (isxdigit(ch)) {
+        if (is_ascii_hex_digit(ch)) {
             if (inverse)
                 inverse_matched = true;
             else
@@ -656,9 +655,9 @@ ALWAYS_INLINE void OpCode_Compare::compare_character_class(const MatchInput& inp
 ALWAYS_INLINE void OpCode_Compare::compare_character_range(const MatchInput& input, MatchState& state, u32 from, u32 to, u32 ch, bool inverse, bool& inverse_matched)
 {
     if (input.regex_options & AllFlags::Insensitive) {
-        from = tolower(from);
-        to = tolower(to);
-        ch = tolower(ch);
+        from = to_ascii_lowercase(from);
+        to = to_ascii_lowercase(to);
+        ch = to_ascii_lowercase(ch);
     }
 
     if (ch >= from && ch <= to) {
@@ -689,7 +688,7 @@ const Vector<String> OpCode_Compare::variable_arguments_to_string(Optional<Match
 
         if (compare_type == CharacterCompareType::Char) {
             auto ch = m_bytecode->at(offset++);
-            auto is_ascii = isascii(ch) && isprint(ch);
+            auto is_ascii = is_ascii_printable(ch);
             if (is_ascii)
                 result.empend(String::formatted("value='{:c}'", static_cast<char>(ch)));
             else
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Tokenizer.cpp b/Userland/Libraries/LibWeb/CSS/Parser/Tokenizer.cpp
index d15e1664ef3..113b240cded 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Tokenizer.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Tokenizer.cpp
@@ -4,11 +4,11 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/SourceLocation.h>
 #include <AK/Vector.h>
 #include <LibTextCodec/Decoder.h>
 #include <LibWeb/CSS/Parser/Tokenizer.h>
-#include <ctype.h>
 
 #define CSS_TOKENIZER_TRACE 0
 
@@ -20,11 +20,6 @@ static inline void log_parse_error(const SourceLocation& location = SourceLocati
     dbgln_if(CSS_TOKENIZER_TRACE, "Parse error (css tokenization) {} ", location);
 }
 
-static inline bool is_surrogate(u32 code_point)
-{
-    return (code_point & 0xfffff800) == 0xd800;
-}
-
 static inline bool is_quotation_mark(u32 code_point)
 {
     return code_point == 0x22;
@@ -35,24 +30,14 @@ static inline bool is_greater_than_maximum_allowed_code_point(u32 code_point)
     return code_point > 0x10FFFF;
 }
 
-static inline bool is_hex_digit(u32 code_point)
-{
-    return isxdigit(code_point);
-}
-
 static inline bool is_low_line(u32 code_point)
 {
     return code_point == 0x5F;
 }
 
-static inline bool is_non_ascii(u32 code_point)
-{
-    return code_point >= 0x80;
-}
-
 static inline bool is_name_start_code_point(u32 code_point)
 {
-    return isalpha(code_point) || is_non_ascii(code_point) || is_low_line(code_point);
+    return is_ascii_alpha(code_point) || !is_ascii(code_point) || is_low_line(code_point);
 }
 
 static inline bool is_hyphen_minus(u32 code_point)
@@ -62,7 +47,7 @@ static inline bool is_hyphen_minus(u32 code_point)
 
 static inline bool is_name_code_point(u32 code_point)
 {
-    return is_name_start_code_point(code_point) || isdigit(code_point) || is_hyphen_minus(code_point);
+    return is_name_start_code_point(code_point) || is_ascii_digit(code_point) || is_hyphen_minus(code_point);
 }
 
 static inline bool is_non_printable(u32 code_point)
@@ -303,12 +288,12 @@ u32 Tokenizer::consume_escaped_code_point()
 
     auto input = code_point.value();
 
-    if (is_hex_digit(input)) {
+    if (is_ascii_hex_digit(input)) {
         StringBuilder builder;
         builder.append_code_point(input);
 
         size_t counter = 0;
-        while (is_hex_digit(peek_code_point().value()) && counter++ < 5) {
+        while (is_ascii_hex_digit(peek_code_point().value()) && counter++ < 5) {
             builder.append_code_point(next_code_point().value());
         }
 
@@ -317,7 +302,7 @@ u32 Tokenizer::consume_escaped_code_point()
         }
 
         auto unhexed = strtoul(builder.to_string().characters(), nullptr, 16);
-        if (unhexed == 0 || is_surrogate(unhexed) || is_greater_than_maximum_allowed_code_point(unhexed)) {
+        if (unhexed == 0 || is_unicode_surrogate(unhexed) || is_greater_than_maximum_allowed_code_point(unhexed)) {
             return REPLACEMENT_CHARACTER;
         }
 
@@ -378,14 +363,14 @@ CSSNumber Tokenizer::consume_a_number()
 
     for (;;) {
         auto digits = peek_code_point().value();
-        if (!isdigit(digits))
+        if (!is_ascii_digit(digits))
             break;
 
         repr.append_code_point(next_code_point().value());
     }
 
     auto maybe_number = peek_twin().value();
-    if (is_full_stop(maybe_number.first) && isdigit(maybe_number.second)) {
+    if (is_full_stop(maybe_number.first) && is_ascii_digit(maybe_number.second)) {
         repr.append_code_point(next_code_point().value());
         repr.append_code_point(next_code_point().value());
 
@@ -393,7 +378,7 @@ CSSNumber Tokenizer::consume_a_number()
 
         for (;;) {
             auto digits = peek_code_point();
-            if (digits.has_value() && !isdigit(digits.value()))
+            if (digits.has_value() && !is_ascii_digit(digits.value()))
                 break;
 
             repr.append_code_point(next_code_point().value());
@@ -403,12 +388,12 @@ CSSNumber Tokenizer::consume_a_number()
     auto maybe_exp = peek_triplet().value();
     if (is_E(maybe_exp.first) || is_e(maybe_exp.first)) {
         if (is_plus_sign(maybe_exp.second) || is_hyphen_minus(maybe_exp.second)) {
-            if (isdigit(maybe_exp.third)) {
+            if (is_ascii_digit(maybe_exp.third)) {
                 repr.append_code_point(next_code_point().value());
                 repr.append_code_point(next_code_point().value());
                 repr.append_code_point(next_code_point().value());
             }
-        } else if (isdigit(maybe_exp.second)) {
+        } else if (is_ascii_digit(maybe_exp.second)) {
             repr.append_code_point(next_code_point().value());
             repr.append_code_point(next_code_point().value());
         }
@@ -417,7 +402,7 @@ CSSNumber Tokenizer::consume_a_number()
 
         for (;;) {
             auto digits = peek_code_point().value();
-            if (!isdigit(digits))
+            if (!is_ascii_digit(digits))
                 break;
 
             repr.append_code_point(next_code_point().value());
@@ -588,19 +573,19 @@ bool Tokenizer::starts_with_a_number() const
 bool Tokenizer::starts_with_a_number(U32Triplet values)
 {
     if (is_plus_sign(values.first) || is_hyphen_minus(values.first)) {
-        if (isdigit(values.second))
+        if (is_ascii_digit(values.second))
             return true;
 
-        if (is_full_stop(values.second) && isdigit(values.third))
+        if (is_full_stop(values.second) && is_ascii_digit(values.third))
             return true;
 
         return false;
     }
 
     if (is_full_stop(values.first))
-        return isdigit(values.second);
+        return is_ascii_digit(values.second);
 
-    if (isdigit(values.first))
+    if (is_ascii_digit(values.first))
         return true;
 
     return false;
@@ -902,7 +887,7 @@ Token Tokenizer::consume_a_token()
         return create_new_token(Token::TokenType::CloseCurly);
     }
 
-    if (isdigit(input)) {
+    if (is_ascii_digit(input)) {
         dbgln_if(CSS_TOKENIZER_TRACE, "is digit");
         reconsume_current_input_code_point();
         return consume_a_numeric_token();
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index b9887a85535..27c8ba5bb07 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -6,6 +6,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/StringBuilder.h>
 #include <AK/Utf8View.h>
 #include <LibCore/Timer.h>
@@ -53,7 +54,6 @@
 #include <LibWeb/Page/BrowsingContext.h>
 #include <LibWeb/SVG/TagNames.h>
 #include <LibWeb/UIEvents/MouseEvent.h>
-#include <ctype.h>
 
 namespace Web::DOM {
 
@@ -253,7 +253,7 @@ String Document::title() const
     StringBuilder builder;
     bool last_was_space = false;
     for (auto code_point : Utf8View(raw_title)) {
-        if (isspace(code_point)) {
+        if (is_ascii_space(code_point)) {
             last_was_space = true;
         } else {
             if (last_was_space && !builder.is_empty())
diff --git a/Userland/Libraries/LibWeb/HTML/Parser/HTMLTokenizer.cpp b/Userland/Libraries/LibWeb/HTML/Parser/HTMLTokenizer.cpp
index 7d716a8532b..638ba37bea1 100644
--- a/Userland/Libraries/LibWeb/HTML/Parser/HTMLTokenizer.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Parser/HTMLTokenizer.cpp
@@ -4,13 +4,13 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/SourceLocation.h>
 #include <LibTextCodec/Decoder.h>
 #include <LibWeb/HTML/Parser/Entities.h>
 #include <LibWeb/HTML/Parser/HTMLToken.h>
 #include <LibWeb/HTML/Parser/HTMLTokenizer.h>
-#include <ctype.h>
 #include <string.h>
 
 namespace Web::HTML {
@@ -93,25 +93,25 @@ namespace Web::HTML {
     if (!current_input_character.has_value())
 
 #define ON_ASCII_ALPHA \
-    if (current_input_character.has_value() && isalpha(current_input_character.value()))
+    if (current_input_character.has_value() && is_ascii_alpha(current_input_character.value()))
 
 #define ON_ASCII_ALPHANUMERIC \
-    if (current_input_character.has_value() && isalnum(current_input_character.value()))
+    if (current_input_character.has_value() && is_ascii_alphanumeric(current_input_character.value()))
 
 #define ON_ASCII_UPPER_ALPHA \
-    if (current_input_character.has_value() && current_input_character.value() >= 'A' && current_input_character.value() <= 'Z')
+    if (current_input_character.has_value() && is_ascii_upper_alpha(current_input_character.value()))
 
 #define ON_ASCII_LOWER_ALPHA \
-    if (current_input_character.has_value() && current_input_character.value() >= 'a' && current_input_character.value() <= 'z')
+    if (current_input_character.has_value() && is_ascii_lower_alpha(current_input_character.value()))
 
 #define ON_ASCII_DIGIT \
-    if (current_input_character.has_value() && isdigit(current_input_character.value()))
+    if (current_input_character.has_value() && is_ascii_digit(current_input_character.value()))
 
 #define ON_ASCII_HEX_DIGIT \
-    if (current_input_character.has_value() && isxdigit(current_input_character.value()))
+    if (current_input_character.has_value() && is_ascii_hex_digit(current_input_character.value()))
 
 #define ON_WHITESPACE \
-    if (current_input_character.has_value() && strchr("\t\n\f ", current_input_character.value()))
+    if (current_input_character.has_value() && is_ascii(current_input_character.value()) && "\t\n\f "sv.contains(current_input_character.value()))
 
 #define ANYTHING_ELSE if (1)
 
@@ -172,26 +172,6 @@ static inline void log_parse_error(const SourceLocation& location = SourceLocati
     dbgln_if(TOKENIZER_TRACE_DEBUG, "Parse error (tokenization) {}", location);
 }
 
-static inline bool is_surrogate(u32 code_point)
-{
-    return (code_point & 0xfffff800) == 0xd800;
-}
-
-static inline bool is_noncharacter(u32 code_point)
-{
-    return code_point >= 0xfdd0 && (code_point <= 0xfdef || (code_point & 0xfffe) == 0xfffe) && code_point <= 0x10ffff;
-}
-
-static inline bool is_c0_control(u32 code_point)
-{
-    return code_point <= 0x1f;
-}
-
-static inline bool is_control(u32 code_point)
-{
-    return is_c0_control(code_point) || (code_point >= 0x7f && code_point <= 0x9f);
-}
-
 Optional<u32> HTMLTokenizer::next_code_point()
 {
     if (m_utf8_iterator == m_utf8_view.end())
@@ -322,7 +302,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.tag_name.append(tolower(current_input_character.value()));
+                    m_current_token.m_tag.tag_name.append(to_ascii_lowercase(current_input_character.value()));
                     m_current_token.m_end_position = nth_last_position(0);
                     continue;
                 }
@@ -458,7 +438,7 @@ _StartOfFunction:
                 ON_ASCII_UPPER_ALPHA
                 {
                     create_new_token(HTMLToken::Type::DOCTYPE);
-                    m_current_token.m_doctype.name.append(tolower(current_input_character.value()));
+                    m_current_token.m_doctype.name.append(to_ascii_lowercase(current_input_character.value()));
                     m_current_token.m_doctype.missing_name = false;
                     SWITCH_TO(DOCTYPEName);
                 }
@@ -507,7 +487,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_doctype.name.append(tolower(current_input_character.value()));
+                    m_current_token.m_doctype.name.append(to_ascii_lowercase(current_input_character.value()));
                     continue;
                 }
                 ON(0)
@@ -550,10 +530,10 @@ _StartOfFunction:
                 }
                 ANYTHING_ELSE
                 {
-                    if (toupper(current_input_character.value()) == 'P' && consume_next_if_match("UBLIC", CaseSensitivity::CaseInsensitive)) {
+                    if (to_ascii_uppercase(current_input_character.value()) == 'P' && consume_next_if_match("UBLIC", CaseSensitivity::CaseInsensitive)) {
                         SWITCH_TO(AfterDOCTYPEPublicKeyword);
                     }
-                    if (toupper(current_input_character.value()) == 'S' && consume_next_if_match("YSTEM", CaseSensitivity::CaseInsensitive)) {
+                    if (to_ascii_uppercase(current_input_character.value()) == 'S' && consume_next_if_match("YSTEM", CaseSensitivity::CaseInsensitive)) {
                         SWITCH_TO(AfterDOCTYPESystemKeyword);
                     }
                     log_parse_error();
@@ -1068,7 +1048,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.attributes.last().local_name_builder.append_code_point(tolower(current_input_character.value()));
+                    m_current_token.m_tag.attributes.last().local_name_builder.append_code_point(to_ascii_lowercase(current_input_character.value()));
                     continue;
                 }
                 ON(0)
@@ -1558,7 +1538,7 @@ _StartOfFunction:
 
                     if (consumed_as_part_of_an_attribute() && !match.value().entity.ends_with(';')) {
                         auto next_code_point = peek_code_point(0);
-                        if (next_code_point.has_value() && (next_code_point.value() == '=' || isalnum(next_code_point.value()))) {
+                        if (next_code_point.has_value() && (next_code_point.value() == '=' || is_ascii_alphanumeric(next_code_point.value()))) {
                             FLUSH_CODEPOINTS_CONSUMED_AS_A_CHARACTER_REFERENCE;
                             SWITCH_TO_RETURN_STATE;
                         }
@@ -1720,14 +1700,14 @@ _StartOfFunction:
                     log_parse_error();
                     m_character_reference_code = 0xFFFD;
                 }
-                if (is_surrogate(m_character_reference_code)) {
+                if (is_unicode_surrogate(m_character_reference_code)) {
                     log_parse_error();
                     m_character_reference_code = 0xFFFD;
                 }
-                if (is_noncharacter(m_character_reference_code)) {
+                if (is_unicode_noncharacter(m_character_reference_code)) {
                     log_parse_error();
                 }
-                if (m_character_reference_code == 0xd || (is_control(m_character_reference_code) && !isspace(m_character_reference_code))) {
+                if (m_character_reference_code == 0xd || (is_unicode_control(m_character_reference_code) && !is_ascii_space(m_character_reference_code))) {
                     log_parse_error();
                     constexpr struct {
                         u32 number;
@@ -1870,7 +1850,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.tag_name.append(tolower(current_input_character.value()));
+                    m_current_token.m_tag.tag_name.append(to_ascii_lowercase(current_input_character.value()));
                     m_temporary_buffer.append(current_input_character.value());
                     continue;
                 }
@@ -1980,7 +1960,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.tag_name.append(tolower(current_input_character.value()));
+                    m_current_token.m_tag.tag_name.append(to_ascii_lowercase(current_input_character.value()));
                     m_temporary_buffer.append(current_input_character.value());
                     continue;
                 }
@@ -2193,7 +2173,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.tag_name.append(tolower(current_input_character.value()));
+                    m_current_token.m_tag.tag_name.append(to_ascii_lowercase(current_input_character.value()));
                     m_temporary_buffer.append(current_input_character.value());
                     continue;
                 }
@@ -2247,7 +2227,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_temporary_buffer.append(tolower(current_input_character.value()));
+                    m_temporary_buffer.append(to_ascii_lowercase(current_input_character.value()));
                     EMIT_CURRENT_CHARACTER;
                 }
                 ON_ASCII_LOWER_ALPHA
@@ -2393,7 +2373,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_temporary_buffer.append(tolower(current_input_character.value()));
+                    m_temporary_buffer.append(to_ascii_lowercase(current_input_character.value()));
                     EMIT_CURRENT_CHARACTER;
                 }
                 ON_ASCII_LOWER_ALPHA
@@ -2512,7 +2492,7 @@ _StartOfFunction:
                 }
                 ON_ASCII_UPPER_ALPHA
                 {
-                    m_current_token.m_tag.tag_name.append(tolower(current_input_character.value()));
+                    m_current_token.m_tag.tag_name.append(to_ascii_lowercase(current_input_character.value()));
                     m_temporary_buffer.append(current_input_character.value());
                     continue;
                 }
@@ -2598,7 +2578,7 @@ bool HTMLTokenizer::consume_next_if_match(const StringView& string, CaseSensitiv
         // FIXME: This should be more Unicode-aware.
         if (case_sensitivity == CaseSensitivity::CaseInsensitive) {
             if (code_point.value() < 0x80) {
-                if (tolower(code_point.value()) != tolower(string[i]))
+                if (to_ascii_lowercase(code_point.value()) != to_ascii_lowercase(string[i]))
                     return false;
                 continue;
             }
diff --git a/Userland/Libraries/LibWeb/Layout/TextNode.cpp b/Userland/Libraries/LibWeb/Layout/TextNode.cpp
index c5aaeb47d8d..6f7818c55fd 100644
--- a/Userland/Libraries/LibWeb/Layout/TextNode.cpp
+++ b/Userland/Libraries/LibWeb/Layout/TextNode.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/ScopeGuard.h>
 #include <AK/StringBuilder.h>
 #include <LibGfx/Painter.h>
@@ -13,7 +14,6 @@
 #include <LibWeb/Layout/Label.h>
 #include <LibWeb/Layout/TextNode.h>
 #include <LibWeb/Page/BrowsingContext.h>
-#include <ctype.h>
 
 namespace Web::Layout {
 
@@ -30,7 +30,7 @@ TextNode::~TextNode()
 static bool is_all_whitespace(const StringView& string)
 {
     for (size_t i = 0; i < string.length(); ++i) {
-        if (!isspace(string[i]))
+        if (!is_ascii_space(string[i]))
             return false;
     }
     return true;
@@ -116,7 +116,7 @@ void TextNode::compute_text_for_rendering(bool collapse, bool previous_is_empty_
     auto it = utf8_view.begin();
     auto skip_over_whitespace = [&] {
         auto prev = it;
-        while (it != utf8_view.end() && isspace(*it)) {
+        while (it != utf8_view.end() && is_ascii_space(*it)) {
             prev = it;
             ++it;
         }
@@ -125,7 +125,7 @@ void TextNode::compute_text_for_rendering(bool collapse, bool previous_is_empty_
     if (previous_is_empty_or_ends_in_whitespace)
         skip_over_whitespace();
     for (; it != utf8_view.end(); ++it) {
-        if (!isspace(*it)) {
+        if (!is_ascii_space(*it)) {
             builder.append(utf8_view.as_string().characters_without_null_termination() + utf8_view.byte_offset_of(it), it.code_point_length_in_bytes());
         } else {
             builder.append(' ');
@@ -160,7 +160,7 @@ void TextNode::split_into_lines_by_rules(InlineFormattingContext& context, Layou
 
         float chunk_width;
         if (do_wrap_lines) {
-            if (do_collapse && isspace(*chunk.view.begin()) && line_boxes.last().is_empty_or_ends_in_whitespace()) {
+            if (do_collapse && is_ascii_space(*chunk.view.begin()) && line_boxes.last().is_empty_or_ends_in_whitespace()) {
                 // This is a non-empty chunk that starts with collapsible whitespace.
                 // We are at either at the start of a new line, or after something that ended in whitespace,
                 // so we don't need to contribute our own whitespace to the line. Skip over it instead!
@@ -264,7 +264,7 @@ TextNode::ChunkIterator::ChunkIterator(StringView const& text, LayoutMode layout
     , m_start_of_chunk(m_utf8_view.begin())
     , m_iterator(m_utf8_view.begin())
 {
-    m_last_was_space = !text.is_empty() && isspace(*m_utf8_view.begin());
+    m_last_was_space = !text.is_empty() && is_ascii_space(*m_utf8_view.begin());
 }
 
 Optional<TextNode::Chunk> TextNode::ChunkIterator::next()
@@ -286,7 +286,7 @@ Optional<TextNode::Chunk> TextNode::ChunkIterator::next()
                 return result.release_value();
         }
         if (m_wrap_lines) {
-            bool is_space = isspace(*m_iterator);
+            bool is_space = is_ascii_space(*m_iterator);
             if (is_space != m_last_was_space) {
                 m_last_was_space = is_space;
                 if (auto result = try_commit_chunk(m_iterator, false); result.has_value())
diff --git a/Userland/Services/WindowServer/Menu.cpp b/Userland/Services/WindowServer/Menu.cpp
index 2af35fb7946..f878ab1035a 100644
--- a/Userland/Services/WindowServer/Menu.cpp
+++ b/Userland/Services/WindowServer/Menu.cpp
@@ -12,6 +12,7 @@
 #include "Screen.h"
 #include "Window.h"
 #include "WindowManager.h"
+#include <AK/CharacterTypes.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/CharacterBitmap.h>
 #include <LibGfx/Font.h>
@@ -20,7 +21,6 @@
 #include <LibGfx/Triangle.h>
 #include <WindowServer/ClientConnection.h>
 #include <WindowServer/WindowClientEndpoint.h>
-#include <ctype.h>
 
 namespace WindowServer {
 
@@ -631,14 +631,14 @@ void Menu::set_visible(bool visible)
 void Menu::add_item(NonnullOwnPtr<MenuItem> item)
 {
     if (auto alt_shortcut = find_ampersand_shortcut_character(item->text())) {
-        m_alt_shortcut_character_to_item_indices.ensure(tolower(alt_shortcut)).append(m_items.size());
+        m_alt_shortcut_character_to_item_indices.ensure(to_ascii_lowercase(alt_shortcut)).append(m_items.size());
     }
     m_items.append(move(item));
 }
 
 const Vector<size_t>* Menu::items_with_alt_shortcut(u32 alt_shortcut) const
 {
-    auto it = m_alt_shortcut_character_to_item_indices.find(tolower(alt_shortcut));
+    auto it = m_alt_shortcut_character_to_item_indices.find(to_ascii_lowercase(alt_shortcut));
     if (it == m_alt_shortcut_character_to_item_indices.end())
         return nullptr;
     return &it->value;
diff --git a/Userland/Services/WindowServer/Window.cpp b/Userland/Services/WindowServer/Window.cpp
index 8eba0a07e2e..3f0bb32f26a 100644
--- a/Userland/Services/WindowServer/Window.cpp
+++ b/Userland/Services/WindowServer/Window.cpp
@@ -13,8 +13,8 @@
 #include "Screen.h"
 #include "WindowManager.h"
 #include <AK/Badge.h>
+#include <AK/CharacterTypes.h>
 #include <WindowServer/WindowClientEndpoint.h>
-#include <ctype.h>
 
 namespace WindowServer {
 
@@ -461,7 +461,7 @@ void Window::handle_keydown_event(const KeyEvent& event)
     if (event.modifiers() == Mod_Alt && event.code_point() && menubar()) {
         Menu* menu_to_open = nullptr;
         menubar()->for_each_menu([&](Menu& menu) {
-            if (tolower(menu.alt_shortcut_character()) == tolower(event.code_point())) {
+            if (to_ascii_lowercase(menu.alt_shortcut_character()) == to_ascii_lowercase(event.code_point())) {
                 menu_to_open = &menu;
                 return IterationDecision::Break;
             }
diff --git a/Userland/Shell/Shell.cpp b/Userland/Shell/Shell.cpp
index aa985d8e7d4..d7069dd6543 100644
--- a/Userland/Shell/Shell.cpp
+++ b/Userland/Shell/Shell.cpp
@@ -7,6 +7,7 @@
 #include "Shell.h"
 #include "Execution.h"
 #include "Formatter.h"
+#include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
 #include <AK/Function.h>
 #include <AK/LexicalPath.h>
@@ -1188,10 +1189,8 @@ Shell::SpecialCharacterEscapeMode Shell::special_character_escape_mode(u32 code_
         return SpecialCharacterEscapeMode::QuotedAsEscape;
     default:
         // FIXME: Should instead use unicode's "graphic" property (categories L, M, N, P, S, Zs)
-        if (code_point < NumericLimits<i32>::max()) {
-            if (isascii(static_cast<i32>(code_point)))
-                return isprint(static_cast<i32>(code_point)) ? SpecialCharacterEscapeMode::Untouched : SpecialCharacterEscapeMode::QuotedAsHex;
-        }
+        if (is_ascii(code_point))
+            return is_ascii_printable(code_point) ? SpecialCharacterEscapeMode::Untouched : SpecialCharacterEscapeMode::QuotedAsHex;
         return SpecialCharacterEscapeMode::Untouched;
     }
 }