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SRT vs TTML: Which Caption Format Should You Use?

Use SRT for simple subtitles and broad compatibility. Use TTML when a broadcaster, streaming platform, or delivery specification explicitly requires it.

Quick Answer

Use SRT for everything that doesn’t require TTML — YouTube, editors, hardware players, and web (via VTT conversion). Use TTML when a platform or broadcaster specifies it: Amazon Prime Video delivery, Apple HLS streams, EBU-TT for European TV, or IMSC-based caption workflows.

Fix SRT file SRT → VTT for web

Use SRT if…

Uploading to YouTube, Vimeo, or most platforms
Working with video editing software
Distributing subtitle files for download
Any general-purpose subtitling workflow

Use TTML if…

A broadcaster or platform requires TTML/DFXP
Delivering to Amazon Prime Video or Apple HLS
Using EBU-TT for European TV delivery
Needing XML-based structured caption metadata

What Is TTML?

TTML (Timed Text Markup Language) is a W3C XML-based caption format. Its file extension is .ttml or .xml. DFXP (Distribution Format Exchange Profile) is a TTML profile used in streaming delivery. Unlike SRT’s plain text, TTML is verbose XML:

<?xml version="1.0" encoding="UTF-8"?>
<tt xml:lang="en" xmlns="http://www.w3.org/ns/ttml">
  <body><div>
    <p begin="00:00:01.000" end="00:00:03.500">Hello, world!</p>
    <p begin="00:00:04.200" end="00:00:07.000">Subtitle two.</p>
  </div></body>
</tt>

TTML supports rich styling, region-based positioning, and metadata. It is an advanced format for professional delivery chains.

SRT vs TTML Comparison Table

Feature	SRT .srt	TTML .ttml/.xml
Format type	Plain text	XML
Standard	De facto	W3C Recommendation
Human-editable	✅ Very easy	Verbose, harder to edit
Styling support	Minimal	Rich (CSS-like attributes)
YouTube upload	✅	✅ (partial styling)
Amazon Prime Video	Not primary	✅ Often required
Apple HLS	Not native	✅
Video editors	✅ Universal	Limited
EBU-TT broadcast	❌	✅
File size	Small	Larger (XML overhead)

When TTML Is Required

OTT platform delivery — Amazon Prime Video, Netflix, Disney+ often specify TTML-derived formats
European broadcast (EBU-TT) — EBU-TT and EBU-TT-D are TTML profiles used in European public broadcasting
Apple HLS / CMAF — Apple’s streaming formats can embed TTML-based subtitle tracks
IMSC — Internet Media Subtitles and Captions, a TTML profile used by BBC, Netflix, and others

For most content creators, YouTubers, and web developers, TTML is never needed.

Frequently Asked Questions

Is TTML the same as DFXP?

DFXP is a specific profile of TTML. They use the same XML structure; DFXP is a constrained subset for cross-platform distribution.

Can I edit TTML files by hand?

Yes, but it is tedious. For simple edits, convert to SRT first, edit, then convert back.

Can YouTube read TTML files?

Yes. YouTube accepts TTML/DFXP with partial styling and positioning support.