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 TTML
Converting a .sub file to .ttml 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 Timed Text Markup Language
Converting a .sub file to .ttml 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.
A .ttml file is a Timed Text Markup Language document: an XML vocabulary in which each <p> element carries begin and end (or dur) attributes plus the caption text. It is the W3C standard that broadcast and streaming systems use as their interchange format for captions and subtitles. For this route the practical draw is a real published standard with formal profiles rather than a de facto convention and expresses styling, layout, and regions that plain caption formats cannot — balanced against far more verbose than SubRip or WebVTT for the same cues, which is worth knowing before you commit a large batch.
Why convert SUB to TTML?
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 .ttml buys you a real published standard with formal profiles rather than a de facto convention, which is why it is the better fit for delivering captions to broadcast and streaming platforms that mandate a TTML profile. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
SUB vs TTML at a glance
| Aspect | MicroDVD subtitles (.sub) | Timed Text Markup Language (.ttml) |
|---|---|---|
| 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 root <tt> element declares the TTML namespace and optional ttp: parameters such as frameRate, tickRate, and timeBase |
| Strongest at | playing back subtitles that were timed against a specific video rip | delivering captions to broadcast and streaming platforms that mandate a TTML profile |
| Weak spot | meaningless without the correct frame rate; the wrong value drifts the whole file | far more verbose than SubRip or WebVTT for the same cues |
| 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 | styling, layout, and region definitions are read past rather than applied: timing and text convert, presentation does not, and no external resource is ever fetched |
Pick TTML as the output
Select .ttml in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if TTML 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 TTML file. Outputs keep the original filename with the .ttml extension.
SUB to TTML questions, answered
Will converting SUB to TTML lose quality?
There is no visual quality to lose — sub is text-oriented and ttml 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 TTML file work?
Broadcast and streaming toolchains — including the DFXP, SMPTE-TT, EBU-TT, and IMSC profiles — read and write TTML, and caption editors such as Subtitle Edit export it. Browsers do not. Novus Convert parses TTML locally with document types and external entities refused outright, resolves all five time-expression shapes, and converts to any of the twelve timed-text targets.
Will the TTML file be bigger or smaller than my SUB?
It depends on the content: the root <tt> element declares the TTML namespace and optional ttp: parameters such as frameRate, tickRate, and timeBase. 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 TTML back to SUB?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .sub → .ttml → .sub is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.