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.

✨ 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

🪄 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.

❓ FAQ

What file types are supported?

The tool supports MP4 video files (.mp4, .mov, .m4v).

Will the quality change after conversion?

No. Only the moov atom is relocated — there is no re-encoding, so quality, file size, and compatibility remain identical.

Are my files sent to a server?

No. All processing happens entirely in your browser. Your video data never leaves your device.

Can I process large files?

Processing depends on your browser's available memory, but the tool works well with most MP4 files.

📦 Results

Drop some MP4 files and the results will appear here.