SRT / VTT / ASS Subtitle Converter

Convert subtitle files and adjust subtitle timelines — Convert between the three most common subtitle formats (SRT, WebVTT, ASS), or adjust a subtitle timeline by shifting every timecode by a fixed number of seconds or scaling them by a playback-speed ratio (e.g. after matching a 1.25x video). Everything runs instantly in your browser as pure JavaScript — no file is uploaded to any server.
Supported input: Subtitle files in SRT / WebVTT / ASS format. Source format is detected automatically. Output is downloaded as UTF-8.
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Click or drag a subtitle file here (SRT / VTT / ASS)

Convert

SRT, VTT and ASS — three subtitle formats

SRT is the simplest: an index, a timestamp pair, text. WebVTT is the web standard — the same core plus styling cues and native <track> support in browsers. ASS (Advanced SubStation Alpha) carries full styling: fonts, colors, screen positioning. Converting down the chain (ASS → SRT) loses styling; converting up adds nothing back — styling must be re-authored.

Timeline shift/scale changes timestamps only — text and format stay untouched.