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 SSA
Converting a .smi file to .ssa 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 SubStation Alpha subtitles
Converting a .smi file to .ssa 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.
An .ssa file is a SubStation Alpha subtitle script — the v4.00 predecessor of Advanced SubStation Alpha. It uses the same [Script Info] / styles / [Events] layout and the same Dialogue timing, with a smaller style table and no v4+ extensions. For this route the practical draw is still rendered by every libass-based player decades later and simpler than the v4+ revision, so easier to parse and hand-edit — balanced against superseded by .ass, which every current authoring tool writes instead, which is worth knowing before you commit a large batch.
Why convert SMI to SSA?
The practical trigger for this conversion is usually a mismatch: with .smi, never formally standardised, so real-world files vary in structure. Switching to .ssa buys you still rendered by every libass-based player decades later, which is why it is the better fit for reading subtitle scripts from late-1990s and early-2000s releases. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
SMI vs SSA at a glance
| Aspect | SAMI captions (.smi) | SubStation Alpha subtitles (.ssa) |
|---|---|---|
| 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 | the [V4 Styles] section uses TertiaryColour and AlphaLevel fields that the later [V4+ Styles] table replaced |
| Strongest at | captioning legacy Windows Media and Silverlight content | reading subtitle scripts from late-1990s and early-2000s releases |
| Weak spot | never formally standardised, so real-world files vary in structure | superseded by .ass, which every current authoring tool writes instead |
| Metadata | style-class and title information describes presentation and language selection, not the cues; conversion keeps timing and text | the v4 style table and script headers describe presentation only; timing and text survive conversion, styling does not |
Pick SSA as the output
Select .ssa in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if SSA 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 SSA file. Outputs keep the original filename with the .ssa extension.
SMI to SSA questions, answered
Will converting SMI to SSA lose quality?
There is no visual quality to lose — smi is text-oriented and ssa 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 SSA file work?
VLC, mpv, and other libass-based players handle .ssa alongside .ass, and Aegisub opens it for editing. No browser renders it. Novus Convert parses the v4 events locally through the same cue model as .ass and exports to any of the twelve timed-text targets.
Will the SSA file be bigger or smaller than my SMI?
It depends on the content: the [V4 Styles] section uses TertiaryColour and AlphaLevel fields that the later [V4+ Styles] table replaced. 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 SSA back to SMI?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .smi → .ssa → .smi is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.