diff --git a/app/logical/ffmpeg.rb b/app/logical/ffmpeg.rb
index 35d0b62f0..fc4612bb2 100644
--- a/app/logical/ffmpeg.rb
+++ b/app/logical/ffmpeg.rb
@@ -83,6 +83,10 @@ class FFmpeg
     frame_count / duration
   end
 
+  def pix_fmt
+    video_stream[:pix_fmt]
+  end
+
   def video_codec
     video_stream[:codec_name]
   end
diff --git a/app/logical/media_file/video.rb b/app/logical/media_file/video.rb
index ac371ced5..0986ed615 100644
--- a/app/logical/media_file/video.rb
+++ b/app/logical/media_file/video.rb
@@ -5,7 +5,7 @@
 #
 # @see https://github.com/streamio/streamio-ffmpeg
 class MediaFile::Video < MediaFile
-  delegate :duration, :frame_count, :frame_rate, :has_audio?, :video_codec, :video_stream, :video_streams, :audio_streams, to: :video
+  delegate :duration, :frame_count, :frame_rate, :has_audio?, :pix_fmt, :video_codec, :video_stream, :video_streams, :audio_streams, to: :video
 
   def dimensions
     [video.width, video.height]
@@ -21,6 +21,17 @@ class MediaFile::Video < MediaFile
     return false if is_webm? && metadata["Matroska:DocType"] != "webm"
     return false if is_mp4? && !video_codec.in?(["h264", "vp9"])
 
+    # Only allow pixel formats supported by most browsers. Don't allow 10-bit video or 4:4:4 subsampling (neither are supported by Firefox).
+    #
+    # yuv420p:  8-bit YUV, 4:2:0 subsampling. The vast majority of videos use this format.
+    # yuvj420p: 8-bit YUV, 4:2:0 subsampling, color range restricted to 16-235. Uncommon, but widely supported.
+    # yuv444p:  8-bit YUV, 4:4:4 subsampling (i.e. no subsampling). Uncommon, not supported by Firefox.
+    # yuv420p10le: 10-bit YUV, 4:2:0 subsampling (i.e. 10-bit video). Uncommon, not supported by Firefox.
+    # gbrp: 8-bit RGB (used by VP9). Uncommon, but widely supported.
+    #
+    # https://github.com/FFmpeg/FFmpeg/blob/master/libavutil/pixfmt.h
+    return false if !pix_fmt.in?(%w[yuv420p yuvj420p gbrp])
+
     true
   end
 
diff --git a/test/files/mp4/README.md b/test/files/mp4/README.md
new file mode 100644
index 000000000..4a47f4b70
--- /dev/null
+++ b/test/files/mp4/README.md
@@ -0,0 +1,6 @@
+Test file sources:
+
+* https://danbooru.donmai.us/posts/2878908 (https://twitter.com/chan_co/status/913025965604749314)
+* https://danbooru.donmai.us/posts/4270949 (https://twitter.com/chrone_co/status/1342709028401643520)
+* https://danbooru.donmai.us/posts/5152189 (https://twitter.com/001_31_/status/1491405055563792386)
+* https://github.com/jursonovicst/gradient/blob/master/player_validation_sequences/test_yuv420p10le_x265.mp4
diff --git a/test/files/mp4/test-300x300-av1.mp4 b/test/files/mp4/test-300x300-av1.mp4
new file mode 100644
index 000000000..17da034b5
Binary files /dev/null and b/test/files/mp4/test-300x300-av1.mp4 differ
diff --git a/test/files/mp4/test-300x300.h265.mp4 b/test/files/mp4/test-300x300-h265.mp4
similarity index 100%
rename from test/files/mp4/test-300x300.h265.mp4
rename to test/files/mp4/test-300x300-h265.mp4
diff --git a/test/files/mp4/test-300x300-vp9.mp4 b/test/files/mp4/test-300x300-vp9.mp4
new file mode 100644
index 000000000..adc8a2d2c
Binary files /dev/null and b/test/files/mp4/test-300x300-vp9.mp4 differ
diff --git a/test/files/mp4/test-300x300-yuv444p-h264.mp4 b/test/files/mp4/test-300x300-yuv444p-h264.mp4
new file mode 100644
index 000000000..76ab8e3da
Binary files /dev/null and b/test/files/mp4/test-300x300-yuv444p-h264.mp4 differ
diff --git a/test/files/mp4/test-300x300-yuvj420p-h264.mp4 b/test/files/mp4/test-300x300-yuvj420p-h264.mp4
new file mode 100644
index 000000000..d1f11d608
Binary files /dev/null and b/test/files/mp4/test-300x300-yuvj420p-h264.mp4 differ
diff --git a/test/files/mp4/test-yuv420p10le-av1.mp4 b/test/files/mp4/test-yuv420p10le-av1.mp4
new file mode 100644
index 000000000..84bcbc297
Binary files /dev/null and b/test/files/mp4/test-yuv420p10le-av1.mp4 differ
diff --git a/test/files/mp4/test-yuv420p10le-h264.mp4 b/test/files/mp4/test-yuv420p10le-h264.mp4
new file mode 100644
index 000000000..18ef037da
Binary files /dev/null and b/test/files/mp4/test-yuv420p10le-h264.mp4 differ
diff --git a/test/files/mp4/test-yuv420p10le-vp9.mp4 b/test/files/mp4/test-yuv420p10le-vp9.mp4
new file mode 100644
index 000000000..0f223f959
Binary files /dev/null and b/test/files/mp4/test-yuv420p10le-vp9.mp4 differ
diff --git a/test/files/webm/test-gbrp-vp9.webm b/test/files/webm/test-gbrp-vp9.webm
new file mode 100644
index 000000000..8388890a8
Binary files /dev/null and b/test/files/webm/test-gbrp-vp9.webm differ
diff --git a/test/files/webm/test-yuv420p10le-vp9.webm b/test/files/webm/test-yuv420p10le-vp9.webm
new file mode 100644
index 000000000..17e5b4de4
Binary files /dev/null and b/test/files/webm/test-yuv420p10le-vp9.webm differ
diff --git a/test/functional/uploads_controller_test.rb b/test/functional/uploads_controller_test.rb
index 7babf6f11..d480ec790 100644
--- a/test/functional/uploads_controller_test.rb
+++ b/test/functional/uploads_controller_test.rb
@@ -243,12 +243,37 @@ class UploadsControllerTest < ActionDispatch::IntegrationTest
         end
 
         should "fail for a .mp4 file encoded with h265" do
-          create_upload!("test/files/mp4/test-300x300.h265.mp4", user: @user)
+          create_upload!("test/files/mp4/test-300x300-h265.mp4", user: @user)
           assert_match("File type is not supported", Upload.last.error)
         end
 
         should "fail for a .mp4 file encoded with av1" do
-          create_upload!("test/files/mp4/test-300x300.av1.mp4", user: @user)
+          create_upload!("test/files/mp4/test-300x300-av1.mp4", user: @user)
+          assert_match("File type is not supported", Upload.last.error)
+        end
+
+        should "fail for a 10-bit color .mp4 file encoded with av1" do
+          create_upload!("test/files/mp4/test-yuv420p10le-av1.mp4", user: @user)
+          assert_match("File type is not supported", Upload.last.error)
+        end
+
+        should "fail for a 10-bit color .mp4 file encoded with h264" do
+          create_upload!("test/files/mp4/test-yuv420p10le-h264.mp4", user: @user)
+          assert_match("File type is not supported", Upload.last.error)
+        end
+
+        should "fail for a 10-bit color .mp4 file encoded with vp9" do
+          create_upload!("test/files/mp4/test-yuv420p10le-vp9.mp4", user: @user)
+          assert_match("File type is not supported", Upload.last.error)
+        end
+
+        should "fail for a 4:4:4 subsampled .mp4 file" do
+          create_upload!("test/files/mp4/test-300x300-yuv444p-h264.mp4", user: @user)
+          assert_match("File type is not supported", Upload.last.error)
+        end
+
+        should "fail for a 10-bit color .webm file encoded with vp9" do
+          create_upload!("test/files/webm/test-yuv420p10le-vp9.webm", user: @user)
           assert_match("File type is not supported", Upload.last.error)
         end
       end
@@ -335,7 +360,7 @@ class UploadsControllerTest < ActionDispatch::IntegrationTest
           assert_equal([550, 368], full_variant.dimensions)
           assert_equal(:jpg, full_variant.file_ext)
 
-          assert_equal(nil, media_asset.variant(:sample))
+          assert_nil(media_asset.variant(:sample))
         end
       end
 
@@ -345,10 +370,12 @@ class UploadsControllerTest < ActionDispatch::IntegrationTest
         should_upload_successfully("test/files/test-static-32x32.gif")
         should_upload_successfully("test/files/test-animated-86x52.gif")
         should_upload_successfully("test/files/mp4/test-300x300.mp4")
-        should_upload_successfully("test/files/mp4/test-300x300.vp9.mp4")
+        should_upload_successfully("test/files/mp4/test-300x300-vp9.mp4")
+        should_upload_successfully("test/files/mp4/test-300x300-yuvj420p-h264.mp4")
         should_upload_successfully("test/files/mp4/test-audio.mp4")
         should_upload_successfully("test/files/mp4/test-audio.m4v")
         should_upload_successfully("test/files/webm/test-512x512.webm")
+        should_upload_successfully("test/files/webm/test-gbrp-vp9.webm")
         # should_upload_successfully("test/files/compressed.swf")
 
         should_upload_successfully("test/files/avif/fox.profile0.8bpc.yuv420.monochrome.avif")
diff --git a/test/unit/media_file_test.rb b/test/unit/media_file_test.rb
index 0e316409c..e79e5d2e3 100644
--- a/test/unit/media_file_test.rb
+++ b/test/unit/media_file_test.rb
@@ -214,16 +214,36 @@ class MediaFileTest < ActiveSupport::TestCase
       assert_equal(10, file.frame_count)
     end
 
+    should "determine the pixel format of the video" do
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-300x300-av1.mp4").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-300x300-h265.mp4").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-300x300-vp9.mp4").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-300x300.mp4").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-audio.m4v").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-audio.mp4").pix_fmt)
+      assert_equal("yuv420p", MediaFile.open("test/files/mp4/test-iso5.mp4").pix_fmt)
+      assert_equal("yuv444p", MediaFile.open("test/files/mp4/test-300x300-yuv444p-h264.mp4").pix_fmt)
+      assert_equal("yuvj420p", MediaFile.open("test/files/mp4/test-300x300-yuvj420p-h264.mp4").pix_fmt)
+      assert_equal("yuv420p10le", MediaFile.open("test/files/mp4/test-yuv420p10le-av1.mp4").pix_fmt)
+      assert_equal("yuv420p10le", MediaFile.open("test/files/mp4/test-yuv420p10le-h264.mp4").pix_fmt)
+      assert_equal("yuv420p10le", MediaFile.open("test/files/mp4/test-yuv420p10le-vp9.mp4").pix_fmt)
+    end
+
     should "detect corrupt videos" do
       assert_equal(true, MediaFile.open("test/files/mp4/test-corrupt.mp4").is_corrupt?)
     end
 
     should "detect supported files" do
       assert_equal(true, MediaFile.open("test/files/mp4/test-300x300.mp4").is_supported?)
-      assert_equal(true, MediaFile.open("test/files/mp4/test-300x300.vp9.mp4").is_supported?)
+      assert_equal(true, MediaFile.open("test/files/mp4/test-300x300-vp9.mp4").is_supported?)
+      assert_equal(true, MediaFile.open("test/files/mp4/test-300x300-yuvj420p-h264.mp4").is_supported?)
 
-      assert_equal(false, MediaFile.open("test/files/mp4/test-300x300.h265.mp4").is_supported?)
-      assert_equal(false, MediaFile.open("test/files/mp4/test-300x300.av1.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-300x300-h265.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-300x300-av1.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-300x300-yuv444p-h264.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-yuv420p10le-av1.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-yuv420p10le-h264.mp4").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/mp4/test-yuv420p10le-vp9.mp4").is_supported?)
     end
   end
 
@@ -235,10 +255,12 @@ class MediaFileTest < ActiveSupport::TestCase
       assert_equal(10, file.frame_count)
     end
 
-    should "not detect .mkv files as .webm" do
-      file = MediaFile.open("test/files/webm/test-512x512.mkv")
+    should "detect supported files" do
+      assert_equal(true, MediaFile.open("test/files/webm/test-512x512.webm").is_supported?)
+      assert_equal(true, MediaFile.open("test/files/webm/test-gbrp-vp9.webm").is_supported?)
 
-      assert_equal(false, file.is_supported?)
+      assert_equal(false, MediaFile.open("test/files/webm/test-512x512.mkv").is_supported?)
+      assert_equal(false, MediaFile.open("test/files/webm/test-yuv420p10le-vp9.webm").is_supported?)
     end
   end