diff --git a/Tests/LibWeb/TestMimeSniff.cpp b/Tests/LibWeb/TestMimeSniff.cpp
index 160254fbe05..c09a080df83 100644
--- a/Tests/LibWeb/TestMimeSniff.cpp
+++ b/Tests/LibWeb/TestMimeSniff.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2023-2024, Kemal Zebari <kemalzebra@gmail.com>.
+ * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -330,3 +331,36 @@ TEST_CASE(determine_computed_mime_type_given_text_or_binary_context)
                                                                                      }));
     EXPECT_EQ("application/octet-stream"sv, MUST(computed_mime_type.serialized()));
 }
+
+TEST_CASE(determine_minimised_mime_type)
+{
+    HashMap<StringView, StringView> mime_type_to_minimised_mime_type_map;
+
+    // JavaScript MIME types should always be "text/javascript".
+    mime_type_to_minimised_mime_type_map.set("text/javascript"sv, "text/javascript"sv);
+    mime_type_to_minimised_mime_type_map.set("application/javascript"sv, "text/javascript"sv);
+    mime_type_to_minimised_mime_type_map.set("text/javascript; charset=utf-8"sv, "text/javascript"sv);
+
+    // JSON MIME types should always be "application/json".
+    mime_type_to_minimised_mime_type_map.set("application/json"sv, "application/json"sv);
+    mime_type_to_minimised_mime_type_map.set("text/json"sv, "application/json"sv);
+    mime_type_to_minimised_mime_type_map.set("application/json; charset=utf-8"sv, "application/json"sv);
+
+    // SVG MIME types should always be "image/svg+xml".
+    mime_type_to_minimised_mime_type_map.set("image/svg+xml"sv, "image/svg+xml"sv);
+    mime_type_to_minimised_mime_type_map.set("image/svg+xml; charset=utf-8"sv, "image/svg+xml"sv);
+
+    // XML MIME types should always be "application/xml".
+    mime_type_to_minimised_mime_type_map.set("application/xml"sv, "application/xml"sv);
+    mime_type_to_minimised_mime_type_map.set("text/xml"sv, "application/xml"sv);
+    mime_type_to_minimised_mime_type_map.set("application/xml; charset=utf-8"sv, "application/xml"sv);
+
+    // MIME types not supported by the user-agent should return an empty string.
+    mime_type_to_minimised_mime_type_map.set("application/java-archive"sv, ""sv);
+    mime_type_to_minimised_mime_type_map.set("application/zip"sv, ""sv);
+
+    for (auto const& mime_type_to_minimised_mime_type : mime_type_to_minimised_mime_type_map) {
+        auto mime_type = MUST(Web::MimeSniff::MimeType::parse(mime_type_to_minimised_mime_type.key)).release_value();
+        EXPECT_EQ(mime_type_to_minimised_mime_type.value, Web::MimeSniff::minimise_a_supported_mime_type(mime_type));
+    }
+}
diff --git a/Userland/Libraries/LibWeb/MimeSniff/MimeType.cpp b/Userland/Libraries/LibWeb/MimeSniff/MimeType.cpp
index 0cfd663ad5b..11cad3bb2cd 100644
--- a/Userland/Libraries/LibWeb/MimeSniff/MimeType.cpp
+++ b/Userland/Libraries/LibWeb/MimeSniff/MimeType.cpp
@@ -2,6 +2,7 @@
  * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
  * Copyright (c) 2022-2023, Linus Groh <linusg@serenityos.org>
  * Copyright (c) 2022, networkException <networkexception@serenityos.org>
+ * Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -369,4 +370,29 @@ bool MimeType::is_json() const
     return subtype().ends_with_bytes("+json"sv) || essence().is_one_of("application/json"sv, "text/json"sv);
 }
 
+// https://mimesniff.spec.whatwg.org/#minimize-a-supported-mime-type
+String minimise_a_supported_mime_type(MimeType const& mime_type)
+{
+    // 1. If mimeType is a JavaScript MIME type, then return "text/javascript".
+    if (mime_type.is_javascript())
+        return "text/javascript"_string;
+
+    // 2. If mimeType is a JSON MIME type, then return "application/json".
+    if (mime_type.is_json())
+        return "application/json"_string;
+
+    // 3. If mimeType’s essence is "image/svg+xml", then return "image/svg+xml".
+    if (mime_type.essence() == "image/svg+xml")
+        return "image/svg+xml"_string;
+
+    // 4. If mimeType is an XML MIME type, then return "application/xml".
+    if (mime_type.is_xml())
+        return "application/xml"_string;
+
+    // FIXME: 5. If mimeType is supported by the user agent, then return mimeType’s essence.
+
+    // 6. Return the empty string.
+    return {};
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/MimeSniff/MimeType.h b/Userland/Libraries/LibWeb/MimeSniff/MimeType.h
index d914616a856..40695cf6f1d 100644
--- a/Userland/Libraries/LibWeb/MimeSniff/MimeType.h
+++ b/Userland/Libraries/LibWeb/MimeSniff/MimeType.h
@@ -67,4 +67,6 @@ private:
     String m_cached_essence;
 };
 
+String minimise_a_supported_mime_type(MimeType const&);
+
 }