This caption conversion utility transforms SubRip (.srt) subtitle files into W3C WebVTT (.vtt) format in real time. WebVTT is the standard caption and subtitle format specified by the W3C for native HTML5 <video> elements and modern web media players.

### SRT vs. WebVTT Specification Differences While both formats organize subtitles into sequential timed cues, key technical distinctions prevent raw SRT files from working in HTML5 video tracks:

- **File Header Signature:** WebVTT files must start with the `WEBVTT` file signature string on the first line, followed by an empty line. - **Timestamp Delimiters:** In SubRip files, millisecond values are separated from seconds using a comma (e.g. `00:00:01,500`). In WebVTT, milliseconds must be separated by a period (e.g. `00:00:01.500`). - **Cue Identifiers:** Sequential numeric identifiers are strictly required in SRT, whereas they are optional in WebVTT.

### Conversion Logic The converter normalizes caption blocks and rewrites timecodes in client-side memory: $\text{Output} = \text{'WEBVTT\n\n'} + \text{srtText.replace}(/(\d{2}:\d{2}:\d{2}),(\d{3})/g, \text{'$1.$2'})

### Concrete Conversion Example **Input SubRip (SRT):** ``` 1 00:00:01,000 --> 00:00:04,000 Welcome to Ubify Tools!

2 00:00:04,500 --> 00:00:08,000 Over 600+ client-side web utilities. ```

**Output WebVTT (VTT):** ``` WEBVTT

1 00:00:01.000 --> 00:00:04.000 Welcome to Ubify Tools!

2 00:00:04.500 --> 00:00:08.000 Over 600+ client-side web utilities. ```

### Privacy and Client-Side Execution All text parsing and regular expression replacements execute entirely within local browser memory. No subtitle scripts, transcripts, or video files are sent to remote servers.