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.
WebVTT is SRT rebuilt for the web: the same cue structure, a WEBVTT header line, a dot instead of a comma before the milliseconds, and optional positioning settings after the timestamp. It is the only subtitle format HTML5 video natively understands.
A file from the DivX years being put on a modern web page — the longest jump on this site, and the one where the frame rate does the most damage if it is wrong. MicroDVD stores frame numbers, so the conversion has to reconstruct real times before a browser can use them, and a rate that is off by a few percent produces captions that start well and drift visibly by the end of a long video. Convert, then scrub to the last minute of the file and check a line there before you publish.
You want WebVTT because the subtitle has to work in a browser. An HTML5 <track> element reads VTT and nothing else, and HLS and DASH streams expect it too. If you are putting a video on your own site, or feeding a web player, this is the conversion that makes captions appear at all.
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.
A file from the DivX years being put on a modern web page — the longest jump on this site, and the one where the frame rate does the most damage if it is wrong. MicroDVD stores frame numbers, so the conversion has to reconstruct real times before a browser can use them, and a rate that is off by a few percent produces captions that start well and drift visibly by the end of a long video. Convert, then scrub to the last minute of the file and check a line there before you publish.
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.