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 ASS
Converting a .smi file to .ass 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 Advanced SubStation Alpha subtitles
Converting a .smi file to .ass 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 .ass file is an Advanced SubStation Alpha subtitle script: an INI-like document whose [Events] section holds Dialogue lines with start and end times, a named style, and text that may carry inline override tags. It is the format fansub and anime communities standardised on because it can position, colour, and animate captions rather than only time them. For this route the practical draw is the most expressive plain-text subtitle format in common use and precise positioning and per-style typography that SubRip cannot express — balanced against styling and positioning are lost the moment the file is converted to SubRip, WebVTT, or a lyric format, which is worth knowing before you commit a large batch.
Why convert SMI to ASS?
The practical trigger for this conversion is usually a mismatch: with .smi, never formally standardised, so real-world files vary in structure. Switching to .ass buys you the most expressive plain-text subtitle format in common use, which is why it is the better fit for styled and positioned captions muxed into Matroska releases. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
SMI vs ASS at a glance
| Aspect | SAMI captions (.smi) | Advanced SubStation Alpha subtitles (.ass) |
|---|---|---|
| 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 script is divided into [Script Info], [V4+ Styles], and [Events] sections, each with its own Format line naming the fields that follow |
| Strongest at | captioning legacy Windows Media and Silverlight content | styled and positioned captions muxed into Matroska releases |
| Weak spot | never formally standardised, so real-world files vary in structure | styling and positioning are lost the moment the file is converted to SubRip, WebVTT, or a lyric format |
| Metadata | style-class and title information describes presentation and language selection, not the cues; conversion keeps timing and text | script metadata and the style table describe presentation rather than the cues themselves; conversion keeps timing and text and reports styling as lost, because no caption target can carry it |
Pick ASS as the output
Select .ass in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if ASS 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 ASS file. Outputs keep the original filename with the .ass extension.
SMI to ASS questions, answered
Will converting SMI to ASS lose quality?
There is no visual quality to lose — smi is text-oriented and ass 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 ASS file work?
VLC, mpv, MPC-HC, and anything else built on libass render .ass faithfully, and Aegisub remains the standard authoring tool. Browsers and most streaming platforms do not accept it, which is why converting to WebVTT or SubRip is the usual delivery step. Novus Convert reads the [Events] dialogue cues locally, strips override tags to plain text, and writes any of the twelve timed-text targets.
Will the ASS file be bigger or smaller than my SMI?
It depends on the content: the script is divided into [Script Info], [V4+ Styles], and [Events] sections, each with its own Format line naming the fields that follow. 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 ASS back to SMI?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .smi → .ass → .smi is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.