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 ITT
Converting a .sub file to .itt 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 iTunes Timed Text
Converting a .sub file to .itt 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 .itt file is an iTunes Timed Text document: a constrained TTML profile that Apple defined for subtitle delivery to the iTunes Store and Apple TV. Its defining trait is timing — cues are addressed in SMPTE timecode (HH:MM:SS:FF) against a frame rate declared in the document header. For this route the practical draw is frame-accurate timing that lines up exactly with an edit timeline and a narrow, validatable profile with far fewer interoperability surprises than full TTML — balanced against frame timecodes are meaningless without the declared frame rate, so a mis-set header shifts every cue, which is worth knowing before you commit a large batch.
Why convert SUB to ITT?
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 .itt buys you frame-accurate timing that lines up exactly with an edit timeline, which is why it is the better fit for delivering subtitles to Apple's ingest specifications. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
SUB vs ITT at a glance
| Aspect | MicroDVD subtitles (.sub) | iTunes Timed Text (.itt) |
|---|---|---|
| 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 | timing is frame-accurate: begin and end are HH:MM:SS:FF timecodes resolved against ttp:frameRate, optionally scaled by ttp:frameRateMultiplier for drop-frame rates such as 23.976 |
| Strongest at | playing back subtitles that were timed against a specific video rip | delivering subtitles to Apple's ingest specifications |
| Weak spot | meaningless without the correct frame rate; the wrong value drifts the whole file | frame timecodes are meaningless without the declared frame rate, so a mis-set header shifts every cue |
| 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 frame-rate parameters are read because timing depends on them; styling attributes are dropped, since millisecond caption targets have nowhere to record them |
Pick ITT as the output
Select .itt in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if ITT 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 ITT file. Outputs keep the original filename with the .itt extension.
SUB to ITT questions, answered
Will converting SUB to ITT lose quality?
There is no visual quality to lose — sub is text-oriented and itt 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 ITT file work?
Final Cut Pro, Compressor, and Apple's delivery pipelines read and write .itt, and Subtitle Edit imports it. Browsers and consumer players do not. Novus Convert resolves the SMPTE timecodes against the document's own ttp:frameRate and ttp:frameRateMultiplier — falling back to 30 fps only when neither is declared — and exports to any of the twelve timed-text targets.
Will the ITT file be bigger or smaller than my SUB?
It depends on the content: timing is frame-accurate: begin and end are HH:MM:SS:FF timecodes resolved against ttp:frameRate, optionally scaled by ttp:frameRateMultiplier for drop-frame rates such as 23.976. 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 ITT back to SUB?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .sub → .itt → .sub is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.