Sync Subtitles — Fix Progressive Drift
When a flat shift isn't enough: give us two reference points and we re-time the entire subtitle linearly, on your device.
Your subtitles and videos never leave your device — everything is processed locally in your browser.
Drop the out-of-sync subtitle
We stretch the timeline using your two reference points
Pick one line near the start and one near the end. Accepts 01:02:03,456 / 95.5 / 95000ms.
Frequently asked questions
Are my subtitle and video files uploaded to a server?
No. SubFix is 100% client-side: parsing, converting, syncing and even burning subtitles all happen inside your browser using JavaScript and WebAssembly. Your files never leave your device.
Which subtitle formats are supported?
SubFix reads and writes SRT, WebVTT (VTT), ASS, SSA and SBV (YouTube), and can also export plain TXT transcripts. Format detection is automatic.
How does hardcoding subtitles work without a server?
SubFix loads FFmpeg compiled to WebAssembly (about 32 MB, only when you use the burn tool) and renders subtitles onto the video frames locally. It works offline once loaded, but is slower than a desktop app — best for short clips.
Is SubFix really free?
Yes — free forever, no sign-up, no watermarks, no file-size games. Because your device does the work, our costs stay near zero.