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 ASS
Converting a .sub 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 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 Advanced SubStation Alpha subtitles
Converting a .sub file to .ass 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 .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 SUB to ASS?
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 .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.
SUB vs ASS at a glance
| Aspect | MicroDVD subtitles (.sub) | 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 | each cue is one line: {startFrame}{endFrame} followed by the text, with | separating multiple display lines | 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 | playing back subtitles that were timed against a specific video rip | styled and positioned captions muxed into Matroska releases |
| Weak spot | meaningless without the correct frame rate; the wrong value drifts the whole file | styling and positioning are lost the moment the file is converted to SubRip, WebVTT, or a lyric format |
| 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 | 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.
SUB to ASS questions, answered
Will converting SUB to ASS lose quality?
There is no visual quality to lose — sub 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 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 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 SUB?
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 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 ASS back to SUB?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .sub → .ass → .sub is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.