diff --git a/Tests/LibWeb/TestMimeSniff.cpp b/Tests/LibWeb/TestMimeSniff.cpp
index a4be94e66c..1bb1a0e324 100644
--- a/Tests/LibWeb/TestMimeSniff.cpp
+++ b/Tests/LibWeb/TestMimeSniff.cpp
@@ -50,6 +50,16 @@ static void set_image_type_mappings(HashMap<StringView, Vector<StringView>>& mim
     mime_type_to_headers_map.set("image/jpeg"sv, { "\xFF\xD8\xFF"sv });
 }
 
+static void set_audio_or_video_type_mappings(HashMap<StringView, Vector<StringView>>& mime_type_to_headers_map)
+{
+    mime_type_to_headers_map.set("audio/aiff"sv, { "FORM\x00\x00\x00\x00\x41IFF"sv });
+    mime_type_to_headers_map.set("audio/mpeg"sv, { "ID3"sv });
+    mime_type_to_headers_map.set("application/ogg"sv, { "OggS\x00"sv });
+    mime_type_to_headers_map.set("audio/midi"sv, { "MThd\x00\x00\x00\x06"sv });
+    mime_type_to_headers_map.set("video/avi"sv, { "RIFF\x00\x00\x00\x00\x41\x56\x49\x20"sv });
+    mime_type_to_headers_map.set("audio/wave"sv, { "RIFF\x00\x00\x00\x00WAVE"sv });
+}
+
 TEST_CASE(determine_computed_mime_type_in_both_none_and_browsing_sniffing_context)
 {
     HashMap<StringView, Vector<StringView>> mime_type_to_headers_map;
@@ -85,13 +95,8 @@ TEST_CASE(determine_computed_mime_type_in_both_none_and_browsing_sniffing_contex
                                                  });
 
     set_image_type_mappings(mime_type_to_headers_map);
+    set_audio_or_video_type_mappings(mime_type_to_headers_map);
 
-    mime_type_to_headers_map.set("audio/aiff"sv, { "FORM\x00\x00\x00\x00\x41IFF"sv });
-    mime_type_to_headers_map.set("audio/mpeg"sv, { "ID3"sv });
-    mime_type_to_headers_map.set("application/ogg"sv, { "OggS\x00"sv });
-    mime_type_to_headers_map.set("audio/midi"sv, { "MThd\x00\x00\x00\x06"sv });
-    mime_type_to_headers_map.set("video/avi"sv, { "RIFF\x00\x00\x00\x00\x41\x56\x49\x20"sv });
-    mime_type_to_headers_map.set("audio/wave"sv, { "RIFF\x00\x00\x00\x00WAVE"sv });
     mime_type_to_headers_map.set("application/x-gzip"sv, { "\x1F\x8B\x08"sv });
     mime_type_to_headers_map.set("application/zip"sv, { "PK\x03\x04"sv });
     mime_type_to_headers_map.set("application/x-rar-compressed"sv, { "Rar\x20\x1A\x07\x00"sv });
@@ -159,3 +164,41 @@ TEST_CASE(determine_computed_mime_type_in_image_sniffing_context)
 
     EXPECT_EQ(mime_type, computed_mime_type.essence());
 }
+
+TEST_CASE(determine_computed_mime_type_in_audio_or_video_sniffing_context)
+{
+    // Cover case where supplied type is an XML MIME type.
+    auto mime_type = "application/rss+xml"sv;
+    auto supplied_type = MUST(Web::MimeSniff::MimeType::parse(mime_type)).release_value();
+    auto computed_mime_type = MUST(Web::MimeSniff::Resource::sniff(""sv.bytes(), Web::MimeSniff::SniffingConfiguration {
+                                                                                     .sniffing_context = Web::MimeSniff::SniffingContext::AudioOrVideo,
+                                                                                     .supplied_type = supplied_type,
+                                                                                 }));
+
+    EXPECT_EQ(mime_type, MUST(computed_mime_type.serialized()));
+    HashMap<StringView, Vector<StringView>> mime_type_to_headers_map;
+
+    set_audio_or_video_type_mappings(mime_type_to_headers_map);
+
+    // Also consider a resource that is not an audio or video.
+    mime_type_to_headers_map.set("application/octet-stream"sv, { "\x00"sv });
+
+    for (auto const& mime_type_to_headers : mime_type_to_headers_map) {
+        auto mime_type = mime_type_to_headers.key;
+
+        for (auto const& header : mime_type_to_headers.value) {
+            auto computed_mime_type = MUST(Web::MimeSniff::Resource::sniff(header.bytes(), Web::MimeSniff::SniffingConfiguration { .sniffing_context = Web::MimeSniff::SniffingContext::AudioOrVideo }));
+            EXPECT_EQ(mime_type, computed_mime_type.essence());
+        }
+    }
+
+    // Cover case where we aren't dealing with an audio or video MIME type.
+    mime_type = "text/html"sv;
+    supplied_type = MUST(Web::MimeSniff::MimeType::parse("text/html"sv)).release_value();
+    computed_mime_type = MUST(Web::MimeSniff::Resource::sniff(""sv.bytes(), Web::MimeSniff::SniffingConfiguration {
+                                                                                .sniffing_context = Web::MimeSniff::SniffingContext::AudioOrVideo,
+                                                                                .supplied_type = supplied_type,
+                                                                            }));
+
+    EXPECT_EQ(mime_type, computed_mime_type.essence());
+}
diff --git a/Userland/Libraries/LibWeb/MimeSniff/Resource.cpp b/Userland/Libraries/LibWeb/MimeSniff/Resource.cpp
index 60e693ab90..d4fa09a626 100644
--- a/Userland/Libraries/LibWeb/MimeSniff/Resource.cpp
+++ b/Userland/Libraries/LibWeb/MimeSniff/Resource.cpp
@@ -540,6 +540,8 @@ ErrorOr<void> Resource::context_specific_sniffing_algorithm(SniffingContext snif
 
     if (sniffing_context == SniffingContext::Image)
         return rules_for_sniffing_images_specifically();
+    if (sniffing_context == SniffingContext::AudioOrVideo)
+        return rules_for_sniffing_audio_or_video_specifically();
 
     return {};
 }
@@ -576,4 +578,36 @@ ErrorOr<void> Resource::rules_for_sniffing_images_specifically()
     return {};
 }
 
+// https://mimesniff.spec.whatwg.org/#sniffing-in-an-audio-or-video-context
+ErrorOr<void> Resource::rules_for_sniffing_audio_or_video_specifically()
+{
+    // 1. If the supplied MIME type is an XML MIME type, the computed MIME type is the supplied MIME type.
+    //    Abort these steps.
+    // NOTE: Non-standard but due to the mime type detection algorithm we need this sanity check.
+    if (m_supplied_mime_type.has_value() && m_supplied_mime_type->is_xml()) {
+        m_computed_mime_type = m_supplied_mime_type.value();
+        return {};
+    }
+
+    // 2. Let audio-or-video-type-matched be the result of executing the audio or video type pattern matching
+    //    algorithm with the resource header as the byte sequence to be matched.
+    auto audio_or_video_type_matched = TRY(match_an_audio_or_video_type_pattern(resource_header()));
+
+    // 3. If audio-or-video-type-matched is not undefined, the computed MIME type is audio-or-video-type-matched.
+    //    Abort these steps.
+    if (audio_or_video_type_matched.has_value()) {
+        m_computed_mime_type = audio_or_video_type_matched.release_value();
+        return {};
+    }
+
+    // 4. The computed MIME type is the supplied MIME type.
+    // NOTE: Non-standard but due to the mime type detection algorithm we need this sanity check.
+    if (m_supplied_mime_type.has_value()) {
+        m_computed_mime_type = m_supplied_mime_type.value();
+    }
+
+    // NOTE: Non-standard but if the supplied mime type is undefined, we use computed mime type's default value.
+    return {};
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/MimeSniff/Resource.h b/Userland/Libraries/LibWeb/MimeSniff/Resource.h
index 826e49a4d8..17a89221f4 100644
--- a/Userland/Libraries/LibWeb/MimeSniff/Resource.h
+++ b/Userland/Libraries/LibWeb/MimeSniff/Resource.h
@@ -13,7 +13,8 @@ namespace Web::MimeSniff {
 enum class SniffingContext {
     None,
     Browsing,
-    Image
+    Image,
+    AudioOrVideo
 };
 
 struct SniffingConfiguration {
@@ -42,6 +43,7 @@ private:
     ErrorOr<void> mime_type_sniffing_algorithm();
     ErrorOr<void> context_specific_sniffing_algorithm(SniffingContext sniffing_context);
     ErrorOr<void> rules_for_sniffing_images_specifically();
+    ErrorOr<void> rules_for_sniffing_audio_or_video_specifically();
 
     // https://mimesniff.spec.whatwg.org/#supplied-mime-type
     // A supplied MIME type, the MIME type determined by the supplied MIME type detection algorithm.