STL to SMI Converter
Fast. Private. Perfect.
100% local processing in your browser. No upload. No waiting. No limits.
Drag & drop your STL file here
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Supports .stl 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 STL to SMI Converter
Our STL to SMI converter reads Spruce Subtitle input and produces Synchronized Accessible Media Interchange output entirely in your browser. Source STL timing (SMPTE HH:MM:SS:FF frame timecodes) is converted to SMI timing (whole milliseconds (Start=...)). 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
STLSTL (Spruce Subtitle) is a text-based subtitle format used in DVD authoring and some broadcast workflows. Each entry uses comma-separated start and end timecodes followed by the subtitle text, with the pipe character (|) denoting line breaks. This text STL variant is distinct from the binary EBU STL broadcast format.
Output Format
SMISMI (SAMI, Synchronized Accessible Media Interchange) is a Microsoft subtitle format using HTML-like <SYNC> elements with Start times in milliseconds. SMI supports multiple language tracks through CSS classes and is suitable for Windows Media Player and legacy accessibility workflows.
Features
Why Convert?
Format Differences
Common Use Cases
Windows Media Captions
Produce SMI captions for Windows Media Player and Microsoft-based playback environments.
Accessibility
Deliver SAMI accessibility captions for legacy corporate and educational media systems.
Multi-Language Files
Use SMI's CSS classes to carry multiple language tracks in a single caption file.
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.
TTML (Timed Text Markup Language)
The streaming alternative: convert to TTML for Netflix, Apple TV, or broadcast delivery.
Frequently Asked Questions
It reads a Spruce Subtitle file, parses each cue's timing and text, normalizes the structure for Synchronized Accessible Media Interchange, and writes a valid .smi file. Source STL timing (SMPTE HH:MM:SS:FF frame timecodes) is converted to SMI timing (whole milliseconds (Start=...)).
Absolutely. Every conversion runs client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.
STL and SMI 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 STL timing (SMPTE HH:MM:SS:FF frame timecodes) is converted to SMI timing (whole milliseconds (Start=...)).
Yes. The converter is fully responsive and works in any modern mobile browser on iOS and Android.