diff --git a/Userland/Libraries/LibCore/MimeData.cpp b/Userland/Libraries/LibCore/MimeData.cpp
index 0ac8c695763..ff7068ba5ed 100644
--- a/Userland/Libraries/LibCore/MimeData.cpp
+++ b/Userland/Libraries/LibCore/MimeData.cpp
@@ -115,6 +115,7 @@ static Array const s_registered_mime_type = {
     MimeType { .name = "image/bmp"sv, .common_extensions = { ".bmp"sv }, .description = "BMP image data"sv, .magic_bytes = Vector<u8> { 'B', 'M' } },
     MimeType { .name = "image/gif"sv, .common_extensions = { ".gif"sv }, .description = "GIF image data"sv, .magic_bytes = Vector<u8> { 'G', 'I', 'F', '8', '7', 'a' } },
     MimeType { .name = "image/gif"sv, .common_extensions = { ".gif"sv }, .description = "GIF image data"sv, .magic_bytes = Vector<u8> { 'G', 'I', 'F', '8', '9', 'a' } },
+    MimeType { .name = "image/j2c"sv, .common_extensions = { ".j2c"sv, ".j2k"sv }, .description = "JPEG2000 image data codestream"sv, .magic_bytes = Vector<u8> { 0xFF, 0x4F, 0xFF, 0x51 } },
     MimeType { .name = "image/jp2"sv, .common_extensions = { ".jp2"sv, ".jpf"sv, ".jpx"sv }, .description = "JPEG2000 image data"sv, .magic_bytes = Vector<u8> { 0x00, 0x00, 0x00, 0x0C, 0x6A, 0x50, 0x20, 0x20, 0x0D, 0x0A, 0x87, 0x0A } },
     MimeType { .name = "image/jpeg"sv, .common_extensions = { ".jpg"sv, ".jpeg"sv }, .description = "JPEG image data"sv, .magic_bytes = Vector<u8> { 0xFF, 0xD8, 0xFF } },
     MimeType { .name = "image/jxl"sv, .common_extensions = { ".jxl"sv }, .description = "JPEG XL image data"sv, .magic_bytes = Vector<u8> { 0xFF, 0x0A } },
diff --git a/Userland/Libraries/LibGfx/ImageFormats/JPEG2000Loader.cpp b/Userland/Libraries/LibGfx/ImageFormats/JPEG2000Loader.cpp
index 87fea74f8cc..4da0d1b91db 100644
--- a/Userland/Libraries/LibGfx/ImageFormats/JPEG2000Loader.cpp
+++ b/Userland/Libraries/LibGfx/ImageFormats/JPEG2000Loader.cpp
@@ -29,9 +29,8 @@ namespace Gfx {
 // or in a JP2 file, which is a container format based on boxes similar to ISOBMFF.
 
 // This is the marker for the codestream version. We don't support this yet.
-// If we add support, add a second `"image/jp2"` line to MimeData.cpp for this magic number.
 // T.800 Annex A, Codestream syntax, A.2 Information in the marker segments and A.3 Construction of the codestream
-[[maybe_unused]] static constexpr u8 marker_id_string[] = { 0xFF, 0x4F, 0xFF, 0x51 };
+static constexpr u8 marker_id_string[] = { 0xFF, 0x4F, 0xFF, 0x51 };
 
 // This is the marker for the box version.
 // T.800 Annex I, JP2 file format syntax, I.5.1 JPEG 2000 Signature box
@@ -717,6 +716,13 @@ static ErrorOr<void> decode_jpeg2000_header(JPEG2000LoadingContext& context, Rea
     if (!JPEG2000ImageDecoderPlugin::sniff(data))
         return Error::from_string_literal("JPEG2000LoadingContext: Invalid JPEG2000 header");
 
+    if (data.starts_with(marker_id_string)) {
+        context.codestream_data = data;
+        TRY(parse_codestream_main_header(context));
+        context.size = { context.siz.width, context.siz.height };
+        return {};
+    }
+
     auto reader = TRY(Gfx::ISOBMFF::Reader::create(TRY(try_make<FixedMemoryStream>(data))));
     context.boxes = TRY(reader.read_entire_file());
 
@@ -914,7 +920,7 @@ ErrorOr<u32> TagTree::read_value(u32 x, u32 y, Function<ErrorOr<bool>()> const&
 
 bool JPEG2000ImageDecoderPlugin::sniff(ReadonlyBytes data)
 {
-    return data.starts_with(jp2_id_string);
+    return data.starts_with(jp2_id_string) || data.starts_with(marker_id_string);
 }
 
 JPEG2000ImageDecoderPlugin::JPEG2000ImageDecoderPlugin()