Check Subtitle Line Length
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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 line length limit is the largest number of characters a subtitle line may hold. This page measures every line of every cue against the limit in the standard you choose — 42 characters per line in the Netflix Timed Text Style Guide, 37 in the BBC's subtitle guidelines — and lists each line over it, with the length it measured and the sentence the limit was read from. The file is read in your browser, never uploaded, and is not changed.
The count is of visible characters. Styling markup is stripped before anything is measured, so an italic line in an ASS file is counted exactly like the same words in an SRT file, while spaces and punctuation are counted because they take up room on screen. That matters because the limit is about what fits: a line that runs past it reaches the edge of the frame, or gets scaled down, or is cut off by the device the subtitles were made for.
Two things the page does not do. It measures each line on its own, so a cue with two lines of 40 characters is not reported under a limit of 42 even though 80 characters are on screen at once — how many lines a cue may hold is a separate limit in both documents and is not checked here. And it accepts plain text: a .txt file has no timings, so each line is given a two-second slot to give the measurement somewhere to sit, and the report prints those times in the row it lists, where you can see they were not in the file.
Examples
A line three characters over Netflix's limit
Subtitles
1
00:00:01,000 --> 00:00:03,000
I missed the last train home and had to walk.
Back before midnight, you said.
2
00:00:04,000 --> 00:00:06,000
Every night this week?
What the report finds
Lines longer than the limit — 1 found
Severity Cues Start End Measured Limit Clause
Warning 1 00:00:01.000 00:00:03.000 45 characters per line 42 characters per line Netflix Timed Text Style Guide: General Requirements — Line length: maximum 42 characters per line (43–44 only in rare exceptions)
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 42 characters per line
Where it is stated: Line length: maximum 42 characters per line (43–44 only in rare exceptions)
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Duration: maximum duration 7 seconds; Reading speed: 20 characters per second for adult content (17 for children's); Line length: maximum 2 lines per subtitle eventThe first cue's opening line runs to 45 characters and is listed; the second line of that same cue measures 31 and is not. The measured value is the longest line of the cue, so a cue that wraps onto two comfortable lines comes back clean while one overlong line does not.
Two lines of exactly 42 characters
Subtitles
1
00:00:01,000 --> 00:00:04,000
I waited at the station for an hour today.
I waited for you at the station all night.
What the report finds
Lines longer than the limit — Nothing found.
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 42 characters per line
Where it is stated: Line length: maximum 42 characters per line (43–44 only in rare exceptions)
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Duration: maximum duration 7 seconds; Reading speed: 20 characters per second for adult content (17 for children's); Line length: maximum 2 lines per subtitle eventBoth lines sit exactly on the limit, so neither is reported — 84 characters on screen in one cue, entirely allowed, because the limit is per line and not per cue.
The same forty characters under the BBC's 37
Subtitles
1
00:00:01,000 --> 00:00:03,000
We can talk about it all in the morning.
2
00:00:04,000 --> 00:00:06,000
Every night this week?
What the report finds
Lines longer than the limit — 1 found
Severity Cues Start End Measured Limit Clause
Warning 1 00:00:01.000 00:00:03.000 40 characters per line 37 characters per line BBC Subtitle Guidelines — Line length: maximum 37 characters per line
Checked against
Standard: BBC Subtitle Guidelines
Limit: 37 characters per line
Where it is stated: Line length: maximum 37 characters per line
Stated as: Guideline
Not checked by this page: Line length: maximum 2 lines (a third only if no important picture is obscured); Reading speed: 160–180 words per minuteNothing about the file changed, only the standard, and the verdict flipped: 40 characters is comfortably inside Netflix's 42 and three over the BBC's 37. The clause column names the BBC guidelines, which is what tells the two reports apart when the measurements are identical.
A plain text file with no timings
Subtitles
The last train had already gone when I finally left the office.
Every night this week?
What the report finds
Lines longer than the limit — 1 found
Severity Cues Start End Measured Limit Clause
Warning 1 00:00:00.000 00:00:02.000 63 characters per line 42 characters per line Netflix Timed Text Style Guide: General Requirements — Line length: maximum 42 characters per line (43–44 only in rare exceptions)
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 42 characters per line
Where it is stated: Line length: maximum 42 characters per line (43–44 only in rare exceptions)
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Duration: maximum duration 7 seconds; Reading speed: 20 characters per second for adult content (17 for children's); Line length: maximum 2 lines per subtitle eventA transcript rather than a subtitle file, and it is measured anyway: a line is a line whether or not it has a timecode. Only the first line is over 42 characters. The start and end times in the row are a timeline this page invented so the measurement would have somewhere to attach — two seconds per line from zero — and nothing was lost while reading, because a line's length does not depend on the clock.
Frequently asked questions
Which characters are counted when a subtitle line is measured here?
Every visible character, spaces and punctuation included, with any styling markup removed first. That is the only way the same sentence can be measured the same way in twelve different formats: an italic line in ASS carries markup that an SRT line does not, and counting the markup would make the two disagree about a line that looks identical on screen.
Should I check my subtitles against 42 characters or 37?
Whichever document you are answerable to. Both figures are offered here. Netflix's style guide allows 42 characters per line, with 43 and 44 only in rare exceptions, and the BBC's guidelines cap a line at 37. They are different answers to the same question because they were written for different delivery targets, and the report names the document it used, so the number is never unattributed.
Is the limit checked per line or per cue?
Per line. A cue with two lines of 40 characters is not reported under a limit of 42, even though it puts 84 characters on screen at once. How many lines a cue may hold is a separate limit — two in both documents here — and this page does not check it; the basis section names it among the limits it did not check.
Can I check a transcript or plain text file for line length?
Yes, and this is the one page in this category that accepts one. A .txt file holds no timings, so the reader gives each line a two-second slot starting at zero; those times appear in the report rows and exist only to give the measurement somewhere to sit. A line's character count does not depend on the clock, so the verdict on every line is real.
Does checking line length change the line breaks in my file?
No. Nothing is rewritten and the file is not uploaded. If you want the lines re-flowed to a column count, that is a different tool that produces a new subtitle file. This page only tells you which lines are over the limit and by how much.
What is the difference between measuring line length and capping the number of lines?
One is about how wide a line may be, the other about how many lines a cue may hold. Both documents state the two limits separately, and a file can fail either one on its own: a cue can hold two short lines and be fine, or one very long line and be over the limit. This page answers the first question only.
What the check looks for
- The report describes a file; the documents behind its numbers address services and suppliers. Netflix's 42 characters and the BBC's 37 come from style guides written for their own delivery targets, not from law. Whether your subtitles have to satisfy them is a question about your contract or your regulator, and this page does not answer it — it reports which lines measured over which published limit.
- Line length is one of the few properties of a subtitle file that directly costs a viewer something. A line that runs off the edge, or is scaled down until it fits, is unreadable to anyone relying on the text, and hardest for viewers with low vision. That is why both documents treat it as a cap rather than a preference, and why measuring it is a separate page from measuring how fast the text has to be read.
References
- Netflix Timed Text Style Guide: General Requirements — line length: maximum 42 characters per line, with 43 to 44 only in rare exceptions.
- BBC Subtitle Guidelines — line length: maximum 37 characters per line.