Convert an SRT subtitle file to the XML-based TTML/DFXP format broadcast and streaming platforms require for captions, locally in your browser. No upload.
Running locally on your device ...
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
TTML (Timed Text Markup Language, often called DFXP in broadcast contexts) is a W3C standard and the officially required XML markup language for captions on many streaming platforms, broadcasters and content-delivery systems - unlike the simple SRT format, it is built for professional delivery chains. Anyone needing to prepare an SRT file for such a supplier will find the conversion here.
Technically, the tool builds a minimal, valid TTML document: an XML declaration, the <tt> root element with the TTML namespace, and one <p begin="..." end="..."> element per subtitle with times in hours:minutes:seconds.milliseconds format. Multi-line text is marked with <br/>, and special characters like & and < are XML-escaped.
The parser that later reads a TTML file back in deliberately works without a full XML parser (none is available inside this tool's background worker) and specifically covers exactly this <p> element pattern. The whole conversion runs locally in your browser.
| Input formats | SRT |
|---|---|
| Auto-conversion | MP4 |
| Output format | TTML |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: A minimal TTML document is produced with times in the common hours:minutes:seconds.milliseconds format - frame- or tick-based timing, regions, styling or metadata blocks that some TTML profiles additionally support are not produced, since an SRT source does not contain that information anyway.
No, the conversion runs entirely locally in your browser.
Many streaming platforms and broadcasters require TTML/DFXP as the official delivery format for captions instead of the simpler SRT.
It is a minimal, valid TTML document with times and text - some suppliers require additional, profile-specific fields not produced here, which vary by recipient.
Yes, there is the sibling tool "Convert TTML to SRT" for that.
TTML to SRT · SRT to ASS · Convert SRT to VTT · Subtitle to text