SMI to ASS Converter
Fast. Private. Perfect.
100% local processing in your browser. No upload. No waiting. No limits.
Drag & drop your SMI file here
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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 ASS Converter
Our SMI to ASS converter reads Synchronized Accessible Media Interchange input and produces Advanced SubStation Alpha output entirely in your browser. Source SMI timing (whole milliseconds (Start=...)) is converted to ASS timing (H:MM:SS.cc centiseconds). 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
ASSASS (Advanced SubStation Alpha v4+) is a styled subtitle format with [Script Info], [V4+ Styles], and [Events] sections. ASS supports per-character styling via override tags, fonts, colors, alpha transparency, outlines, shadows, blur, screen positioning, vector drawing, and karaoke timing. Timing uses centisecond precision (H:MM:SS.cc).
Features
Why Convert?
Format Differences
Common Use Cases
Styled Subtitles
Create ASS subtitles with fonts, colors, outlines, and positioning for visually rich presentation.
Anime & Karaoke
Produce ASS files for fansubbing and karaoke workflows that rely on override tags and libass rendering.
Aegisub Editing
Generate an ASS file you can open directly in Aegisub for further styling and timing work.
Related Formats
Frequently Asked Questions
It reads a Synchronized Accessible Media Interchange file, parses each cue's timing and text, normalizes the structure for Advanced SubStation Alpha, and writes a valid .ass file. Source SMI timing (whole milliseconds (Start=...)) is converted to ASS timing (H:MM:SS.cc centiseconds).
Absolutely. Every conversion runs client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.
SMI and ASS 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 ASS timing (H:MM:SS.cc centiseconds).
Yes. The converter is fully responsive and works in any modern mobile browser on iOS and Android.