Free, instant, and entirely in your browser — your subtitle file is never uploaded.
MicroDVD counts frames, not seconds — this has to match the video.
MicroDVD is the odd one out: it counts frames, not time. Each line is {start}{end} followed by the text, with a pipe between display lines. There is no timestamp anywhere in the file.
SRT is the plainest subtitle format there is: a number, a start and end time, the lines of text, a blank line, repeat. It came out of a 1990s DVD-ripping program called SubRip and has outlived every format designed to replace it, precisely because there is almost nothing in it to go wrong.
Usually this is a rescue. A .sub file turns up next to an old download and nothing modern will touch it — and even when something does, the timing is wrong because the file was made for a different frame rate. Converting to SRT turns the frame counts into real timestamps once and for all, which also means any error is now frozen into the file. If the result drifts, come back and convert again at a different rate rather than trying to fix it line by line.
You almost certainly want SRT because something refuses to take what you have. It is the format with the fewest ways to be rejected: media players, Plex and Jellyfin libraries, YouTube, Vimeo, editing software and hardware players all read it without complaint. Converting into SRT is the standard move for making a subtitle simply work somewhere.
Both sides carry the same thing — lines of text with a start and an end — so this is the cleanest conversion in the set. Nothing is approximated and nothing is thrown away; the timestamps are rewritten in the target's notation and the text goes across as it stands. What changes is compatibility: which players, platforms and browsers will accept the file you end up with. Because MicroDVD is the source here, the frame rate is something the file does not reliably tell you. The numbers inside it are frame counts, and turning them back into seconds requires the rate the file was authored for. Many of these files declare it on a leading {1}{1} line, and when yours does that value is used automatically. When it does not, the figure above is an assumption — if the result drifts steadily rather than sitting at a constant offset, that assumption is what to change.
No. The conversion runs in your browser using JavaScript — your SUB 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.
Usually this is a rescue. A .sub file turns up next to an old download and nothing modern will touch it — and even when something does, the timing is wrong because the file was made for a different frame rate. Converting to SRT turns the frame counts into real timestamps once and for all, which also means any error is now frozen into the file. If the result drifts, come back and convert again at a different rate rather than trying to fix it line by line.
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 SUB, it says so and points you at the all-format converter instead of producing a broken file.