Subtitles go wrong in two ways. Either every line is early or late by the same amount - fixed with a simple shift - or they start right and drift further out as the film goes on, which almost always means they were timed for a different release, at a different frame rate. This fixes both: shift by any amount, resync from two lines set to the times they should appear (which corrects an offset and a drift together), or convert between frame rates directly.
Add the video and the subtitles play over it as they stand after each change, so you can check a fix before saving; clicking a line jumps the video there. It also removes formatting tags and hearing-impaired notes, trims lines that overlap, and converts between SRT and WebVTT. Files that are not UTF-8 are read as Western European (Windows-1252), or as Cyrillic (Windows-1251) when most of their letters are non-Latin; if the letters still come out wrong, Read as reads the file again as any of 17 encodings, from Greek and Arabic to Chinese, Japanese and Korean. Saved files are always UTF-8.
- How do I know whether to shift or resync?
- Watch the start and the end. If both are out by the same amount, shift. If the start is right but the end is noticeably out - or the gap grows as you go - resync by two lines. Frame rate conversion is the same fix when you already know the two rates, typically 25 and 23.976.
- What happens to lines that would start before the video?
- Shifting earlier can push the first lines before zero. Any line that would finish before the video starts is removed, one that straddles zero is cut to start at zero, and the page says how many were affected. Undo puts them back.
- Can it convert SRT to VTT?
- Yes - open either and save as the other. The text and timing carry over; WebVTT position settings are kept when saving as .vtt and dropped from .srt, which has nowhere to put them.
- Can it convert ASS or SSA to SRT?
- Yes. Open the .ass or .ssa and save it as .srt or .vtt. Each Dialogue line becomes a subtitle with its timing and text, and line breaks are kept; the styling codes in curly brackets, positions, karaoke and drawn shapes are dropped, since SRT and VTT have no way to show them. It cannot save back to ASS.
- How do I delay subtitles by a few seconds?
- Type the delay in seconds in Shift everything - 2.5 makes every line appear 2.5 seconds later, -2.5 earlier - and press Shift, or tap the +1 s and +0.1 s buttons until the lines match the speech. Minutes work too, as 1:30.5. Then save as .srt or .vtt.
- Only part of the film is out of sync. Can I shift just that part?
- Yes. Under Starting from, pick the first line that is wrong, then shift: that line and every one after it move, and the lines before it stay where they were. This is the fix when a release has an extra scene or an ad break the subtitles were not made for.
- The subtitles show strange characters like é or пр. How do I fix them?
- The file was saved in an older encoding than the one it is being read as. Choose the right one under Read as at the top - Cyrillic (Windows-1251) for Russian, Ukrainian or Bulgarian, Central European (Windows-1250) for Polish or Czech, Greek, Turkish, Arabic, Hebrew, Chinese, Japanese or Korean - until the text reads properly, then save: the new file is UTF-8, which every player reads.