Add your SUB file
Drop one or more .sub 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.
SUB to SSA
Converting a .sub 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 SUB 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 MicroDVD subtitles to SubStation Alpha subtitles
Converting a .sub file to .ssa extracts the document's content from its office package into a portable form. A .sub file in the MicroDVD convention is a frame-based subtitle list: every line reads {startFrame}{endFrame}text, with a pipe character separating the lines inside one cue. Because the timing is expressed in frames rather than milliseconds, a MicroDVD file only means anything alongside the frame rate of the video it was timed to.
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player decades later and simpler than the v4+ revision, so easier to parse and hand-edit — balanced against superseded by .ass, which every current authoring tool writes instead, which is worth knowing before you commit a large batch.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 SUB to SSA?
The practical trigger for this conversion is usually a mismatch: with .sub, meaningless without the correct frame rate; the wrong value drifts the whole file. 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.
SUB vs SSA at a glance
| Aspect | MicroDVD subtitles (.sub) | 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 | each cue is one line: {startFrame}{endFrame} followed by the text, with | separating multiple display lines | the [V4 Styles] section uses TertiaryColour and AlphaLevel fields that the later [V4+ Styles] table replaced |
| Strongest at | playing back subtitles that were timed against a specific video rip | reading subtitle scripts from late-1990s and early-2000s releases |
| Weak spot | meaningless without the correct frame rate; the wrong value drifts the whole file | superseded by .ass, which every current authoring tool writes instead |
| Metadata | there is no metadata section; the only header-like content is the frame-rate declaration, which is read on input and written on output | 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.
SUB to SSA questions, answered
Will converting SUB to SSA lose quality?
There is no visual quality to lose — sub 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 SUB files here?
Yes — the .sub 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 SUB?
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 SUB file?
In .sub, there is no metadata section; the only header-like content is the frame-rate declaration, which is read on input and written on output. 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 SUB?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .sub → .ssa → .sub is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.