How it works
- Drop your video and press Make captions, or write your own lines in the list.
- Pick a style and watch the preview on your video.
- Press Burn into video. The encode runs on your device and the MP4 downloads.
Handbrake and ffmpeg do this on a desktop. Here the same ffmpeg engine runs as WebAssembly in the tab, drawing the subtitles with libass, the renderer most video apps use. The font is bundled, so it looks the same on every computer.
The encode is single threaded, which keeps it working in every browser. Plan on about one to three times the clip length. Keep the tab open and in front while it runs, since browsers slow down background tabs.
Audio is kept as AAC. Video is re-encoded to H.264 so it plays on phones, and the original file is left alone. The free export has a small Captionfox mark in the top corner. Subscribers and pack buyers get a clean one.
Questions
Why is it slow on big files?
Everything runs on your own CPU in one thread. A 10 minute 1080p clip can take a while. Shorter and smaller files are quick.
Can I burn in my own SRT?
Not yet. Captions come from the list, and you can type or paste lines into it.