SRT ⇄ VTT Subtitle Converter & Millisecond Sync Shifter

Convert Subtitles Between SRT and WebVTT Flawlessly

Subtitles look like plain text until you try to move them between platforms. YouTube happily takes both SRT and WebVTT, HTML5 video players demand WebVTT, older desktop players prefer SRT — and the two formats disagree on almost every detail that matters. Timestamps use commas in SRT (00:01:23,456) but periods in WebVTT (00:01:23.456). WebVTT requires a WEBVTT header line that SRT forbids. Get any of it wrong and the player silently shows nothing, leaving you wondering whether the file is broken or the video is. The maddening part is the silence: no error message, just a video playing with zero captions and no clue why.

The anatomy is simple once you see it side by side. An SRT cue is a sequence number, a timestamp line with an arrow (00:00:01,000 --> 00:00:04,000), the text lines, then a blank line. WebVTT drops the numbers, keeps the same idea, swaps the comma for a dot, and adds the WEBVTT magic header — plus optional superpowers SRT never had: cue positioning, styling, and chapter metadata. Converting is therefore mostly mechanical: renumber or de-number, swap the decimal separator, add or strip the header. Mechanical, but brutally unforgiving of sloppiness at 3 AM before a launch.

Real-world subtitle files add spice. Auto-generated captions arrive with overlapping timestamps and zero punctuation; ripped subtitles carry HTML-ish tags like <i> that WebVTT handles differently; frame-rate conversions shift every timestamp by a few milliseconds per minute until dialogue drifts visibly out of sync. Always validate after converting: check that the first cue starts when speech starts, that no cue exceeds about 42 characters per line (the readability standard), and that the file is UTF-8 so accented characters and non-Latin scripts survive. A two-minute check here saves an embarrassing re-upload later.