Convert SRT to TTML Online Free

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Convert SRT subtitle files to TTML XML format for broadcast, streaming platforms, and professional subtitle delivery systems. ChangeThisFile generates valid W3C TTML output.

By ChangeThisFile Team · Last updated: March 2026

Quick Answer

ChangeThisFile converts SRT to TTML on a secure server. Upload your SRT subtitle file and it is converted to W3C TTML XML format with proper namespaces and begin/end attributes. Files are auto-deleted after conversion. Free with no signup required.

First daily conversion free No signup required Encrypted transfer · Async jobs kept up to 24h Queued when needed Updated May 2026

SRT vs TTML: Format Comparison

Key differences between the two formats

Feature	SRT	TTML
Structure	Plain text blocks	XML with namespace declarations
Styling	Basic bold/italic tags	Full CSS-like XML attributes
Positioning	Not supported	Named regions with coordinates
File size	Compact	Larger due to XML overhead
Editability	Any text editor	XML editor recommended
Use case	Consumer video players	Broadcast and streaming platforms
Standard	Informal	W3C TTML 1.0 / 2.0

When to Convert

Common scenarios where this conversion is useful

Submitting subtitles to a broadcast delivery system

Many broadcast networks and streaming platforms require TTML for subtitle ingest. Converting SRT to TTML makes your subtitles compatible with professional delivery specifications.

Integrating subtitles into a professional NLE workflow

Professional non-linear editors like Avid Media Composer and Adobe Premiere handle TTML in broadcast production workflows. Converting SRT to TTML bridges the gap from consumer to professional formats.

Distributing subtitles to SMIL-based media servers

TTML is closely related to SMIL and is used in adaptive streaming. Converting SRT to TTML enables subtitle delivery via MPEG-DASH and HLS streams that support TTML side-cars.

Who Uses This Conversion

Tailored guidance for different workflows

Video Editors & Subtitlers

Convert SRT caption files to TTML for the subtitle track your editor or delivery spec requires
Move SRT subtitles into TTML to hand off to an editor working in a different tool

After converting to TTML, confirm the cue timings still line up with the video

Check that line breaks and special characters survived the SRT to TTML conversion

Content Creators & YouTubers

Convert SRT captions to TTML to upload alongside your video on YouTube, Vimeo, or social platforms
Turn a SRT caption file into TTML to make your video clearer and more accessible

Keep individual TTML cues short (about one to two lines) so captions stay readable on screen

Preview the TTML captions on the actual video to catch any timing drift before publishing

Accessibility & Localization Teams

Convert SRT subtitles to TTML to meet the caption format an accessibility or compliance spec requires
Prepare SRT captions as TTML to hand to translators or a localization workflow

Speaker labels and on-screen positioning only carry over if TTML supports them, so spot-check the result

Validate the TTML file in a caption checker to catch overlapping cues or malformed timestamps

How to Convert SRT to TTML

1

Upload your SRT file

Drag and drop your SRT subtitle file onto the converter, or click browse to select it. The upload is encrypted.
2

Server-side conversion

The server parses each SRT cue, converts timestamps to HH:MM:SS.mmm TTML format, and writes a well-formed TTML XML document with standard namespace declarations.
3

Download the TTML

Save your converted TTML file. The server copy is automatically deleted after processing.

Automate this conversion

Convert SRT to TTML via API

Integrate this conversion into your pipeline with 3 lines of code. Free tier: 25 conversions/month.

curl -X POST https://changethisfile.com/v1/convert \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -F "file=@input.srt" \
  -F "target=ttml" \
  -o output.ttml --fail

const form = new FormData();
form.append('file', fileInput.files[0]);
form.append('target', 'ttml');

const res = await fetch('https://changethisfile.com/v1/convert', {
  method: 'POST',
  headers: { 'Authorization': 'Bearer YOUR_API_KEY' },
  body: form
});
const blob = await res.blob(); // your converted TTML file

Replace YOUR_API_KEY with your free key — no credit card needed.

Get a free API key

Frequently Asked Questions

What is TTML format used for?

TTML (Timed Text Markup Language) is the W3C standard for subtitle interchange in professional, broadcast, and streaming contexts. Netflix, Amazon, and Disney+ all use TTML variants internally.

Will the TTML output be W3C standards-compliant?

Yes. The output conforms to W3C TTML 1.0 with standard tt, head, body, div, and p elements and xmlns namespace declarations.

What happens to SRT bold and italic formatting?

SRT HTML tags like <b>, <i>, and <u> are preserved as plain text in the TTML p elements. Mapping them to TTML tts:fontStyle attributes would require additional processing not included in this basic converter.

Can I add TTML region positioning after conversion?

Yes. The output TTML file is valid XML that you can edit in any text or XML editor to add region definitions, styling attributes, and positioning as required by your delivery specification.

What timestamp format does the TTML output use?

The converter outputs HH:MM:SS.mmm format (with a period before milliseconds), which is the standard TTML timeExpression format.

Does this work for Netflix or Amazon subtitle submissions?

Netflix and Amazon use strict TTML profiles (IMSC-1 and IMSC-2) with specific requirements. The converter produces standard TTML that may need additional attributes and styling to meet their exact specs.

Are my files deleted after conversion?

Yes. Files are transferred over HTTPS and automatically deleted after the TTML is ready for download.

Is there a file size limit?

SRT files are plain text. The 50 MB server limit is not a concern for subtitle files.

Can I validate the TTML output?

You can validate the XML well-formedness with any XML parser. For TTML-specific validation, use the W3C's TTML validator or the Inband Caption Test Suite.

Can I convert TTML back to SRT if needed?

Yes. ChangeThisFile supports TTML to SRT conversion for round-tripping between formats.

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