Why do my subtitles drift further out of sync over time?

The subtitles were timed against a different frame rate. PAL releases run at 25 fps and NTSC ones at 23.976 fps, a 4.27% difference that accumulates to more than five minutes over a two-hour film. Convert between the frame rates rather than shifting.

Why do my subtitles show question marks instead of letters?

The file is not UTF-8. Subtitles are often saved as Windows-1251 for Cyrillic, Windows-1252 for Western European, or Big5 and Shift-JIS for Chinese and Japanese. Reading the file with the right encoding fixes it.

Why are my subtitles out of sync?

Q: Why are my subtitles out of sync?

Either every line is off by the same amount, which a constant shift fixes, or the error grows as the video plays, which means the subtitles were made for a different frame rate and need a frame-rate conversion or a two-point stretch.

There are three causes and they need three different fixes. Applying the wrong one is why people end up nudging the same file for twenty minutes. Play the video with the subtitles on, check the start and then the end, and answer one question.

Does the gap stay the same, or get worse?

A constant offset

about 60% of cases

The gap is the same at the start, the middle and the end.

The subtitles were made for a release with a different intro length, or the video was trimmed at the front.

Fix: Shift the whole file by one amount.

Shift the file

Frame-rate drift

about 25% of cases

Fine at the start, several seconds out by the end, and the error grows steadily.

The same film ships at 25 fps in PAL regions and 23.976 fps in NTSC ones. That 4.27% speed difference accumulates to more than five minutes across a two-hour film.

Fix: Convert between the two frame rates, or pin the first and last cue.

Convert frame rate

Uneven drift

about 10% of cases

It wanders. Off by two seconds in one scene, in sync the next, off by five later.

Usually subtitles OCR-ed from hardsubs, or a release with scenes cut at different points.

Fix: Pin one cue near the start and one near the end and stretch between them. If it still wanders, no single correction can fix it and the file needs line-by-line retiming.

Pin two cues

Finding the exact offset

Play the video and pause on a clearly spoken word. Note the time on the player, then note the start time of the subtitle that should match it. The difference is your offset. If the word is spoken at 01:05.500 and the subtitle starts at 01:03.000, the subtitles run 2.5 seconds early and need to move 2.5 seconds later.

You can skip the arithmetic: load the video intothe tooland hold an arrow key until the words line up.

Things that are not a timing problem

The text is question marks or nonsense symbols: That is a character encoding problem, not a timing one. The file is probably Windows-1251, Windows-1252 or Big5 and something read it as UTF-8. Cuelatch detects this on load and lets you correct it.
Nothing shows at all: The player usually has not been pointed at the file. Give the subtitle file the same name as the video, in the same folder, and most players pick it up.
It is only wrong in VLC: VLC's G and H keys shift subtitles during playback, but the change disappears when you close it. To fix the file itself for every player, correct the file.

Cuelatch runs entirely in your browser. Subtitle and video files are never uploaded.