Split an SRT or VTT file into parts

When a file needs splitting

A single subtitle file is the right shape for a single video. Things go wrong when the video changes shape: a long recording is published as three episodes, a stream is cut into chapters, a lecture is posted in parts to fit a platform's length limit, or you only want captions for one segment of a longer piece. The subtitle file for the whole thing then has to be cut at the same points as the video, and each piece has to start at zero because each video does.

Original, split at 10:00 and 20:00:

part 1   00:00:01,000 --> 00:00:03,500     (unchanged)
part 2   00:10:04,000 --> 00:10:06,000     becomes 00:00:04,000 --> 00:00:06,000
part 3   00:21:30,000 --> 00:21:32,500     becomes 00:01:30,000 --> 00:01:32,500

Two ways to choose where to cut

Every so many minutes. Enter a part length and the file is cut at every multiple of it up to the last cue. Ten minutes gives parts at 0:00, 10:00, 20:00 and so on. Parts are numbered in order, and the last one is whatever is left.

At times I choose. Enter the cut points, separated by commas: 10:00, 25:30, 1:02:00. This is the one to use when your video parts are different lengths, so the cuts follow where you actually divided the video.

What counts as being in a part

A cue belongs to the part in which it starts. That means no cue is cut in half and none is duplicated, which is the safe rule for text. The cost is that a cue that starts a second before a cut and runs two seconds past it will be on screen for a second after the next part begins, if the part's video ends exactly at the cut. If your cut points sit in natural pauses, as most chapter breaks do, this never shows. If one does, shorten that cue in the editor.

Downloading the parts

Each part appears as its own card with its name, its cue count, the stretch of the original it came from and Copy and Download buttons. Names use your file's name plus -part-1, -part-2 and so on, in the format you pick. Nothing is zipped, so a phone browser that allows one download at a time still works: press each Download in turn.

Splitting is not the same as re-timing

This tool moves times by exact multiples, so it is right only if the original subtitles were right. If the whole file is a little early or late, fix that first with the time shifter, then split. And if you made the subtitles with Scriptorium, you can instead transcribe each video part on its own, which gives every part subtitles timed from its own audio. transcript file formats explained explains the format underneath.