Add your SMI file
Drop one or more .smi files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
SMI to VTT
Converting a .smi file to .vtt extracts the document's content from its office package into a portable form. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop SMI files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting SAMI captions to WebVTT subtitles
Converting a .smi file to .vtt extracts the document's content from its office package into a portable form. An .smi file is a SAMI caption document: HTML-like markup in which <SYNC Start=…> elements mark the millisecond at which a caption appears, and the caption runs until the next SYNC. Microsoft designed it as an accessibility format, so a single file can carry several languages selected by CSS class.
A .vtt file is a WebVTT caption document: a WEBVTT header followed by timed cues for HTML5 video and audio. It is the web-native caption format browsers expect for the track element. For this route the practical draw is first-class support in modern browsers and richer cue settings than SubRip — balanced against some legacy desktop players prefer .srt and mishandle WebVTT settings, which is worth knowing before you commit a large batch.
Why convert SMI to VTT?
The practical trigger for this conversion is usually a mismatch: with .smi, never formally standardised, so real-world files vary in structure. Switching to .vtt buys you first-class support in modern browsers, which is why it is the better fit for captioning HTML5 video with the track element. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
SMI vs VTT at a glance
| Aspect | SAMI captions (.smi) | WebVTT subtitles (.vtt) |
|---|---|---|
| Format type | Text-based — characters and structure, so there is no visual quality loss | Text-based — characters and structure, so there is no visual quality loss |
| How it stores data | the document has an HTML shape: <SAMI> wrapping <HEAD> with a <STYLE> block and <BODY> with the SYNC elements | files begin with WEBVTT and optional metadata headers before the first blank line |
| Strongest at | captioning legacy Windows Media and Silverlight content | captioning HTML5 video with the track element |
| Weak spot | never formally standardised, so real-world files vary in structure | some legacy desktop players prefer .srt and mishandle WebVTT settings |
Pick VTT as the output
Select .vtt in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if VTT is selectable, the route is real and validated.
Convert on your device
Press Convert. The package is unzipped in memory and its XML content parsed locally; nothing is uploaded.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid VTT file. Outputs keep the original filename with the .vtt extension.
SMI to VTT questions, answered
Will converting SMI to VTT lose quality?
There is no visual quality to lose — smi is text-oriented and vtt is text-oriented, so the question is structural fidelity. Text, ordering, and basic structure are preserved; complex layout, embedded objects, and styling beyond the target's model are simplified.
Is it private to convert SMI files here?
Yes — the .smi file is processed inside your browser tab and never uploaded. The package is unzipped in memory and its XML content parsed locally; nothing is uploaded. Close the tab and the file is gone from memory.
Where will the VTT file work?
Chrome, Firefox, Safari, and Edge render .vtt through HTML track elements. Professional editors and many downloadable players also import it, though SubRip remains more common in older desktop workflows.
Will the VTT file be bigger or smaller than my SMI?
It depends on the content: files begin with WEBVTT and optional metadata headers before the first blank line. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my SMI file?
In .smi, style-class and title information describes presentation and language selection, not the cues; conversion keeps timing and text. Re-encoding through the browser pipeline does not carry embedded metadata into the output, which doubles as a privacy scrub — check the exported file if you specifically need tags preserved.
Can I convert VTT back to SMI?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .smi → .vtt → .smi is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.