MP4 Fast Start Converter
Convert non-progressive MP4 files into Fast Start (web-optimized) form right in your browser. Moves the moov atom to the front so playback can begin while the file is still downloading.
📦 Results
💡 What is Fast Start?
If an MP4's metadata (the moov atom) sits after the video data (mdat), browsers must download the whole file before they can start playing. Moving moov to the front enables progressive playback while the file is still loading.
✨ Features
- Reorders the moov atom to the front so the web can stream the video
- Batch convert multiple files with drag & drop
- No re-encoding — quality, size, and compatibility are preserved
- Automatically rewrites stco / co64 chunk offsets
- Runs entirely in your browser — videos are never uploaded
🪄 Ways to Use It
Embed video on your site
A Fast Start MP4 starts playing before it finishes downloading, making page visits feel much faster.
Progressive direct delivery
Even without HLS or DASH, a moov-at-front file lets viewers seek and stream smoothly over a plain URL.
iOS / Android app assets
AVPlayer and ExoPlayer load the first frame much sooner when the asset is Fast Start.
When you can't use ffmpeg
On machines without CLI access, this tool gives you qt-faststart-equivalent results, browser-only.
🔒 Privacy
Selected videos are processed only in your browser. They are never uploaded to any server.