Free, instant, and entirely in your browser — your subtitle file is never uploaded.
MicroDVD counts frames, not seconds — this has to match the video.
SBV is YouTube's own caption format, and about as simple as SRT with one line less: no sequence number, and the two timestamps separated by a comma rather than an arrow.
ASS is a typesetting language that happens to carry subtitles. Named styles, exact positioning, rotation, fades, karaoke timing and vector drawing all live in the file, split across a [Script Info], a styles and an [Events] section.
Captions that started life in YouTube's editor, on their way to becoming something more considered. This is common when a channel's automatic or volunteer captions become the base for a subtitled release — the timing is already roughly right against the video, which is the expensive part, and ASS is where the styling and the sign work get added. The conversion carries the text and the times exactly; everything ASS can do beyond that is now available and entirely unused.
You want ASS because you are about to typeset, not merely translate. Going into ASS is what opens the door to named styles, exact positioning, fades and karaoke timing in an editor like Aegisub. The conversion does not create any of that — it gives you a clean file with one default style, ready for the work to begin.
The target format can do far more than the source ever could, but a conversion cannot invent design that was never there. What you get is a well-formed file with a single default style — correct, playable, and ready to be styled properly in an editor like Aegisub. The gain is real but it is potential: the capability is now available to you, not already used.
No. The conversion runs in your browser using JavaScript — your SBV file is read from disk, converted in memory and handed back as a download. Nothing is transmitted, so there is nothing for us to store or delete. You can disconnect from the internet after this page loads and the conversion still works.
Captions that started life in YouTube's editor, on their way to becoming something more considered. This is common when a channel's automatic or volunteer captions become the base for a subtitled release — the timing is already roughly right against the video, which is the expensive part, and ASS is where the styling and the sign work get added. The conversion carries the text and the times exactly; everything ASS can do beyond that is now available and entirely unused.
The page checks before it converts. Subtitle formats are identified by what is inside the file rather than by the extension — which matters, because .sub alone is used by three unrelated formats. If you hand this page something that is not SBV, it says so and points you at the all-format converter instead of producing a broken file.