SMI to TTML Subtitle Converter
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100% local processing in your browser. No upload. No waiting.
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Supports .smi, .sami, .html files up to 50 MB
More Subtitle Tools
How It Works
Upload SMI File
Drag & drop or select your .smi file
Convert Instantly
We process it locally in your browser
Download TTML
Get your .ttml file immediately
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.
Free & Local
Each file can be up to 50 MB. Batches can contain up to 200 files or 1 GB total.
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 begin and end timing (seconds, such as 1.500s). SMI styling and markup are stripped, leaving basic 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 a W3C XML subtitle format. TTML stores captions in <p> elements with begin and end timing expressed as seconds or clock values, and the broader format family supports rich styling, regions, and profiles such as IMSC and ITT.
Features
Why Convert?
Format Differences
Common Use Cases
Streaming Delivery
Produce basic TTML subtitles, then add any profile-specific metadata or validation required by your platform.
Professional Interchange
Use TTML as the rich, validatable interchange format for professional timed-text pipelines.
IMSC / ITT Profiles
Start with plain TTML timing and text when preparing files for an IMSC or ITT workflow.
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, strips SMI markup, and writes a basic .ttml file. Source SMI timing (whole milliseconds (Start=...)) is converted to TTML begin and end timing in seconds.
Absolutely. Every conversion runs client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.
SMI styling and markup are dropped. The output is plain timed TTML text without SMI styling or delivery-profile metadata.
Yes, completely free with no sign-up, no watermarks, and files up to 50 MB each. 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.