Find Overlapping Subtitles
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Which frame rate the timings are counted in. On the format pages this is what MicroDVD needs, because it stores timing as frame numbers. On the frame rate pages it is the rate the file was timed against — the version the subtitles were made for — and the page's second box takes the rate of the video you are going to use them with. 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60 are the common ones. Getting it wrong shifts the whole timeline, and on the frame rate pages it shifts it by a ratio rather than by a fixed amount.
Overlapping subtitles are cues that share the screen: a cue that begins before an earlier one has finished. This page finds them and says how much time the two share, in milliseconds, cue by cue. It does not change the file — the original is left exactly as it was, and what you get back is a report you can download as a PDF or as a CSV.
An overlap is not automatically a mistake. Two speakers interrupting each other, a timing pass done by hand, or subtitles converted from another format all produce them, and some of those overlaps are deliberate. What makes them worth listing is that a player cannot draw two cues in the same place at the same time, so what the viewer sees is decided for you and may not be what the file says. The number to look at is the shared milliseconds: an overlap of 400 ms reads as a flicker, while several seconds usually means a cue was pasted in at the wrong place.
The report also says what it could not check. A format that stores no end time cannot be measured for overlaps at all, and a cue whose end was not after its start is repaired while the file is read — that repair is listed at the top of the report rather than being quietly folded into the findings. A file with nothing wrong still produces a report that says so: "checked, nothing found" and "not checkable" are two different sentences, and this page keeps them apart. Everything runs in your browser, and a whole season can go through the queue in one go.
Examples
Two cues sharing a second
Subtitles
1
00:00:01,000 --> 00:00:04,000
First line.
2
00:00:03,000 --> 00:00:06,000
Second line, starting early.
What the report finds
Overlapping cues — 1 found
Severity Cues Start End Measured
Error 1, 2 00:00:03.000 00:00:04.000 1000 ms
The second cue starts while the first is still on screen. The measured value is the shared span — the first cue's end minus the second cue's start — not the length of either cue.
Cues that touch are not overlaps
Subtitles
1
00:00:01,000 --> 00:00:02,000
First line.
2
00:00:02,000 --> 00:00:03,000
Second line, touching.
What the report finds
Overlapping cues — Nothing found
Checks run 1
Cues 2
The second cue starts on the exact millisecond the first one ends. That is correct timing, so nothing is reported — but the report still says the check ran, which is not the same thing as a file that could not be checked.
A cue nested inside a longer one
Subtitles
1
00:00:00,000 --> 00:00:10,000
Long opening line.
2
00:00:01,000 --> 00:00:02,000
Nested inside it.
3
00:00:03,000 --> 00:00:04,000
Also nested inside it.
What the report finds
Overlapping cues — 2 found
Severity Cues Start End Measured
Error 1, 2 00:00:01.000 00:00:02.000 1000 ms
Error 1, 3 00:00:03.000 00:00:04.000 1000 ms
Both of the short cues overlap the long one, and neither overlaps the other. Each comparison is made against the furthest point reached so far, which is why the second short cue is caught even though the cue right before it does not reach it.
Frequently asked questions
What exactly counts as an overlapping cue on this page?
A cue whose start time is earlier than the furthest end time already reached in the file. Cues that merely touch — one ending at 00:00:04,000 and the next starting at 00:00:04,000 — are not overlaps and are never listed. A one-millisecond overlap is listed, because it is one.
Does this tool change my subtitle file?
No. The file is read and a report comes out; not a single timecode is rewritten. Removing overlaps is a separate tool, and keeping the check and the repair apart means the report you hand to somebody describes the original file rather than a version this page already edited.
How is the amount of overlap worked out?
From the start of the later cue to the earlier of the two end times, in milliseconds. For a cue sitting completely inside a longer one the whole of that cue is the overlap. Comparisons run against the furthest end reached so far rather than the cue immediately before, so three cues stacked on the same moment produce two findings rather than one.
Which subtitle formats can be checked for overlaps?
The ten that store both a start and an end time: SRT, WebVTT, ASS, SSA, SBV, SMI, MicroDVD, TTML, JSON and CSV. LRC and plain text are not on the list because they hold one time per line, so there is nothing to compare — a file in one of those formats has to be converted first.
What is in the report I download?
A header naming the file, the format it was read as, the cue count and the frame rate where the format stores frames; a line for anything that had to be repaired while reading; then one section per check, with the cue numbers, both timecodes and the measured milliseconds for every finding. The same content is offered as a PDF to read and as a CSV to sort in a spreadsheet.
Why does a file with overlaps play as though it were fine?
Because the player decides what to draw when two cues land on the same moment, and that decision is not in the file. Some players show the later cue, some stack them, and a positioned cue may sit in a corner where it does not visibly clash. The report tells you what the file actually contains, which is the thing you can fix.
Can I check a whole season in one go?
Yes. Drop all the files in and they are checked one after another, each with its own report, and the reports download together as a zip. Progress is shown per file and the run can be stopped partway without leaving anything behind.