Convert Subtitle Files — Private & Free (VTT → SRT)
SRT, WebVTT, ASS/SSA, SBV and TXT, converted instantly on your device. Nothing is uploaded, ever.
Your subtitles and videos never leave your device — everything is processed locally in your browser.
Drop your subtitle file here
SRT, VTT, ASS, SSA, SBV or TXT — or click to browse
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.