- Ensure that the
moov
(metadata) is before themdat
(audio/video data). This is also called “fast start” or “web optimized”. For example, Handbrake has a “Web Optimized” checkbox, and ffmpeg and avconv have the output option-movflags faststart
. - Ensure that your web server is reporting the correct Content-Type (video/mp4).
- Ensure that your web server is configured to serve byte range requests.
- Ensure that your web server is not applying gzip or deflate compression on top of the compression in the mp4 file.
You can check the headers being sent by your web server using curl -I http://yoursite/video.mp4
or using the developer tools in your browser (Chrome, Firefox) (reload the page if it is cached). The HTTP Response Header should include Content-Type: video/mp4 and Accept-Ranges: bytes, and no Content-Encoding:.