Check Subtitle Maximum Duration
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The limit is not a number you type in: it is read out of a published document, and the report names that document, quotes the sentence it came from, says whether that sentence is a requirement or guidance, and gives the day we last verified it with a link. Pick the document you are answerable to. They do not agree with each other: Netflix counts characters per second and caps a line at 42 characters, while Ofcom and the BBC count words per minute and, on line length, the BBC caps a line at 37. Three of them state no figures at all — 47 CFR §79.1, WCAG 2.2 SC 1.2.2 and EN 301 549, which requires web pages and non-web documents to satisfy that same criterion. Those three require captions to identify who is speaking and to carry non-speech information, and leave every number to the broadcaster; a page that checks them asks whether the file does it, not whether some number is exceeded. They also do not carry the same weight: a defect that reads as a warning against WCAG reads as an error against EN 301 549, because the standard turns that criterion into a shall. Changing this box changes the limit and the citation together, so a report can never carry one document's number under another document's name. Pages that check something only one of these documents states offer only that one.
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.
A cue that stays on screen too long is the other half of the same problem. Seven seconds is the limit in the Netflix Timed Text Style Guide, and this page lists every cue that outlives it, with the duration it measured and the sentence the number came from. The file is read in your browser and is never uploaded; the subtitle file itself is not changed.
Where a cue that is too short is hard to read, a cue that is too long is usually one nobody turned off. It covers whatever is on screen behind it, so a line held for twenty seconds sits over three or four later shots, and if the subtitles are burned into the picture that is what the viewer sees. A cue that outlives its line also keeps the text up after it was said, which reads as the subtitles lagging rather than as a timing mistake.
The two duration limits are separate checks on purpose. A cue can be too long and nothing else, or too short and nothing else, and a single check that looked at one end would leave the other half of the file unreported. An empty file still produces a report: it says the file holds no cues, the check ran, and nothing was found — three separate facts that a report reading nothing found would have collapsed into one.
Examples
A cue held for nine seconds
Subtitles
1
00:00:01,000 --> 00:00:03,000
Where were you last night?
2
00:00:05,000 --> 00:00:14,000
I was working late, and then I went home, and then I could not sleep.
3
00:00:20,000 --> 00:00:22,000
Every night this week?
What the report finds
Cues above the maximum duration — 1 found
Severity Cues Start End Measured Limit Clause
Warning 2 00:00:05.000 00:00:14.000 9000 ms 7000 ms Netflix Timed Text Style Guide: General Requirements — Duration: maximum duration 7 seconds
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 7000 ms
Where it is stated: Duration: maximum duration 7 seconds
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Reading speed: 20 characters per second for adult content (17 for children's); Line length: maximum 42 characters per line (43–44 only in rare exceptions); Line length: maximum 2 lines per subtitle eventThe middle cue runs from five seconds to fourteen and is reported at 9000 ms against a limit of 7000; the short cue before it and the two-second cue after it are not. The same cue is also far too fast to read, which is the usual pairing: text left on screen too long often has more words in it than the reading speed allows, and the reading-speed page is where that half gets measured.
Seven seconds, and one millisecond over
Subtitles
1
00:00:01,000 --> 00:00:08,000
We can talk about it all in the morning.
2
00:00:10,000 --> 00:00:17,001
I was working late, and I did not think you would notice.
What the report finds
Cues above the maximum duration — 1 found
Severity Cues Start End Measured Limit Clause
Warning 2 00:00:10.000 00:00:17.001 7001 ms 7000 ms Netflix Timed Text Style Guide: General Requirements — Duration: maximum duration 7 seconds
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 7000 ms
Where it is stated: Duration: maximum duration 7 seconds
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Reading speed: 20 characters per second for adult content (17 for children's); Line length: maximum 42 characters per line (43–44 only in rare exceptions); Line length: maximum 2 lines per subtitle eventThe first cue sits exactly on seven seconds and is not reported; the second runs one millisecond past it and is. Both halves matter — the first is what stops every correctly timed cue from being listed, the second is what stops a cue the document does not allow from passing because the comparison was written as an upper bound rather than a strict one.
Frequently asked questions
Where does the seven-second maximum on this page come from?
From the Netflix Timed Text Style Guide: General Requirements, which states a maximum duration of seven seconds. It is a delivery requirement in Netflix's supplier contracts rather than law, the report labels it as guidance, and this page checks against it and nothing else: a maximum duration from a different house style would need its own entry in the archive before it could be checked.
Why is a cue that stays up too long worse than one that flashes past?
A short cue costs the viewer one line; a long cue usually costs several later shots. A line held for twenty seconds stays over the picture after it was spoken, and if the file is burned in, it covers whatever the camera moves on to. It is also the defect least likely to be noticed while checking, because nothing looks wrong: the text is there, the timings are not obviously broken, and the drift only shows in the second half of a programme.
Is a cue of exactly seven seconds reported here?
No, and a cue of 7001 milliseconds is. The comparison is strictly greater than the limit, so the boundary value itself is allowed. Putting a cue exactly on the limit on the allowed side is the same call the minimum-duration page makes in the other direction: written the other way round, every correctly timed cue in the file would be listed.
What does the report say about a file with no cues in it?
Three things that are easy to confuse: the file holds zero cues, one check ran, and nothing was found. It also prints the basis section in full, including the limits in that document this page did not check. An empty file is the case where a report that only printed nothing found would mislead most, so the other two sentences stay.
Should I run the minimum and maximum duration checks on the same file?
Yes — they are two ends of one question and neither page covers the other. A cue can be reported by one and not the other, and a file can be inside both. Both pages read the same document, both leave your file untouched, and both reports can be downloaded one after the other in a single batch.
Does checking maximum duration change my subtitle file?
No. Nothing is rewritten and nothing is uploaded. If you want an over-long cue actually split or shortened, that is a different tool that produces a new subtitle file. This page reports which cues are over the limit, how long they ran, and where the limit is written down.
What the check looks for
- The report describes a file, not a service. Netflix's seven seconds is a requirement in its supplier contracts; it is not law, and nothing here says your subtitles satisfy it. What the report states is which cues measured above which published limit, and which of that document's limits this page did not check.
- Over-long cues matter to viewers for the same reason the accessibility rules exist: the text stops matching what is being said, and a viewer who depends on it is left reading a line that no longer corresponds to the picture. That is a comprehension cost rather than a cosmetic one, and it is invisible in a spot check of a file, which is why measuring the whole file is worth a page of its own.
References
- Netflix Timed Text Style Guide: General Requirements — duration: maximum duration 7 seconds.