SRT and VTT are close cousins, not twins
SubRip (.srt) is the oldest, most widely produced caption format — it is what almost every transcription tool, editing app, and download button hands you. WebVTT (.vtt) is the format the web platform actually understands: it is the only caption format the HTML5 <track> element is required to support. The two look nearly identical at a glance, which is exactly why dropping a raw .srt into a <track> tag fails silently — the browser parses the file, hits a line it does not expect, and shows no captions at all.
The three changes this tool makes
The conversion is small and reversible, but every part of it matters. First, a WEBVTT header line is prepended — VTT files that lack it are rejected outright. Second, the decimal separator in every timecode flips from a comma to a dot: SRT writes 00:00:01,000 while VTT requires 00:00:01.000. Third, the bare numeric sequence counter that SRT puts before each cue is stripped, because VTT does not use cue numbers (and a stray number on its own line can confuse a strict parser). Everything else — the text, the line breaks, the timing — is preserved byte-for-byte.
Why this runs entirely in your browser
A subtitle file is plain text, often holding a full transcript of a private call, a customer demo, or unreleased footage. There is no reason for it to touch a server. This tool reads the file directly in your tab with the browser's own FileReader, rewrites the timecodes in memory, and hands you a download — no network request leaves your machine. You can confirm it yourself: open your network tab, run a conversion, and watch it stay empty. The same privacy-first principle drives the rest of Clipy, the free screen recorder these tools were built around.
Skip subtitle wrangling entirely
Converting captions by hand is a chore that exists only because your recording tool did not give you the right format to begin with. Clipy auto-generates captions on every screen recording — transcribed, time-aligned, and ready to play on the share page without you touching a single .srt or .vtt file. If you find yourself round-tripping subtitle formats often, record in Clipy instead and let the captions come with the video for free.