SMI to TTML Converter
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100% local processing in your browser. No upload. No waiting. No limits.
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Supports .smi files up to any size
More Subtitle Tools
Why Choose AllSubConverter?
Your Privacy Matters
Everything runs in your browser. Your files are never uploaded.
Lightning Fast
Optimized processing engine converts files in seconds.
Truly Unlimited
No file size limits. No daily limits. Completely free.
Works Everywhere
Works on Windows, Mac, Linux, iOS, Android - any modern browser.
Free Online SMI to TTML Converter
Our SMI to TTML converter reads Synchronized Accessible Media Interchange input and produces Timed Text Markup Language output entirely in your browser. Source SMI timing (whole milliseconds (Start=...)) is converted to TTML timing (seconds (1.500s) or clock values). Styling and markup that the target format cannot represent are normalized or stripped, leaving valid, ready-to-use output. The conversion runs client-side, so your subtitle files are never uploaded to a server.
Input Format
SMISMI (SAMI, Synchronized Accessible Media Interchange) is a Microsoft subtitle format built from HTML-like <SYNC> elements whose Start attribute is given in milliseconds. SMI supports multiple language tracks through CSS classes and was widely used for Windows Media Player captions and accessibility content.
Output Format
TTMLTTML (Timed Text Markup Language) is an XML-based subtitle format standardized by the W3C and required by Netflix, Apple TV, and broadcast delivery. TTML stores captions in <p> elements with begin/end timing expressed as seconds (1.500s) or clock values, supports rich styling and regions, and is the basis of the IMSC and ITT profiles.
Features
Why Convert?
Format Differences
Common Use Cases
Streaming Delivery
Produce TTML subtitles that meet Netflix, Apple TV, and broadcast delivery specs.
Professional Interchange
Use TTML as the rich, validatable interchange format for professional timed-text pipelines.
IMSC / ITT Profiles
Generate TTML that serves as the basis for IMSC and iTunes Timed Text delivery.
Related Formats
SRT (SubRip)
The universal plain-text alternative: convert to SRT for maximum device compatibility.
VTT (WebVTT)
The web alternative: convert to VTT if your target is HTML5 video or YouTube.
SCC (Scenarist Closed Captioning)
The North American broadcast alternative: convert to SCC for CEA-608 caption delivery.
Frequently Asked Questions
It reads a Synchronized Accessible Media Interchange file, parses each cue's timing and text, normalizes the structure for Timed Text Markup Language, and writes a valid .ttml file. Source SMI timing (whole milliseconds (Start=...)) is converted to TTML timing (seconds (1.500s) or clock values).
Absolutely. Every conversion runs client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.
SMI and TTML both support styling, but their styling models differ. Styling that cannot be mapped is normalized or dropped, while dialogue text and timing are always preserved.
Yes, completely free with no sign-up, no watermarks, and no file size limits. All processing happens in your browser, so your files are never uploaded to a server.
Source SMI timing (whole milliseconds (Start=...)) is converted to TTML timing (seconds (1.500s) or clock values).
Yes. The converter is fully responsive and works in any modern mobile browser on iOS and Android.