screen-recording-mp4

Use ffmpeg with the libx264 encoder: ffmpeg -i input.mov -c:v libx264 -crf 25 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4. This produces a compact H.264 MP4 that plays inline on GitHub and in browsers.

Use H.264 with -crf 25 and -preset medium for a good balance of quality and size, typically reducing the file to 10-20% of the original. Always add -movflags +faststart so the video starts playing immediately when embedded.

H.264 offers the widest compatibility for GitHub and older environments. HEVC (libx265 with -tag:v hvc1) is 30-50% smaller and works in Safari and QuickTime. AV1 is smallest but has less certain playback support, so use it only when explicitly needed.

QuickTime requires the hvc1 tag to recognize HEVC streams in MP4 containers. Re-encode with -tag:v hvc1 added to the ffmpeg command and the file will open correctly in QuickTime and Safari.

The MP4 likely lacks the faststart flag, meaning the moov atom is at the end of the file. Re-encode with -movflags +faststart so browsers can begin playback before downloading the entire video.

The Skill outputs MP4 only, because GIF has color limitations and poor size efficiency for screen recordings. If a GIF is strictly required, it must be handled as a separate one-off request outside the standard flow.