Check Subtitles Against Ofcom Guidance
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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.
Ofcom's guidance for television access services is a short document, and about subtitles it makes one measurable statement: subtitles should not exceed 160 to 180 words per minute. This page runs every subtitle check it has against that document at once — reading speed, line length, minimum and maximum cue duration, and whether speakers are identified — and prints the answer for each, including the answers that are "this document does not say". The file is read in your browser, never uploaded, and is not changed.
What comes back is worth reading in full, because four of the five sections say the same kind of thing and it is not "fine". Ofcom states no limit on how many characters may sit on a line, no minimum and no maximum cue duration, so those three sections read Not applicable — no limit was given, so there is nothing to compare against. The speaker section reads a second, different sentence: this document states no such requirement at all. That second sentence is the whole reason this page exists next to the four single-check pages. A page that checks line length against Netflix can only ever tell you about Netflix; this page tells you which of the five things Ofcom has an opinion about, and Ofcom has an opinion about exactly one of them.
Running it also settles a question people ask in the other direction: whether the check they care about is missing because they picked the wrong document. If a house style says 42 characters a line and Ofcom's guidance says nothing, that number came from somewhere else, and the report's reference list will not be where it lives.
Examples
A file with three cues over 180 words per minute
Subtitles
1
00:00:01,000 --> 00:00:03,000
JOHN: I told you not to wait up.
2
00:00:04,000 --> 00:00:07,400
- I know what you did last summer, and I am not going to pretend otherwise.
- Then say it out loud, right here, in front of everybody.
3
00:00:09,000 --> 00:00:09,600
Wait.
4
00:00:11,000 --> 00:00:19,200
MARY: Nothing. It does not matter now.
5
00:00:21,000 --> 00:00:23,000
The quick brown fox jumps over the lazy dog every single morning.
What the report finds
Cues read faster than the limit — 3 found
Severity Cues Start End Measured Limit Clause
Warning 1 00:00:01.000 00:00:03.000 240 wpm 180 wpm Ofcom: Guidelines on the provision of television access services — Reading speed: subtitles should not exceed 160–180 words per minute
Warning 2 00:00:04.000 00:00:07.400 494.1 wpm 180 wpm (the same sentence)
Warning 5 00:00:21.000 00:00:23.000 360 wpm 180 wpm (the same sentence)
Lines longer than the limit — Not applicable. No limit was given, so there is nothing to compare against
Cues below the minimum duration — Not applicable. No limit was given, so there is nothing to compare against
Cues above the maximum duration — Not applicable. No limit was given, so there is nothing to compare against
Cues with two speakers and no name — Not applicable. This document says nothing about this, so there is no requirement to check against
What it was checked against
Standard: Ofcom access services guidance
Limit: 180 wpm
Where it is stated: Reading speed: subtitles should not exceed 160–180 words per minute
Stated as: Guideline
Verified: 2026-10-16The five sections are the point of this page, and the last four are not a failure to run. Compare this report with the same five cues checked against the Netflix guide: there, three of those sections carry findings, because that document states a line length, a minimum and a maximum. Here they carry a sentence each. The speed is measured in words per minute, counted by whitespace, exactly as Ofcom states it — the report does not convert it into characters per second, because a words-to-characters conversion would be a number the guidance never stated. Note also the last section's wording, which is a different sentence from the three above it: one is "no figure", the other is "no requirement".
A cue sitting exactly on the limit
Subtitles
1
00:00:01,000 --> 00:00:03,000
Where were you going last night?
2
00:00:05,000 --> 00:00:07,000
Where were you going so late tonight?
What the report finds
Cues read faster than the limit — 1 found
Severity Cues Start End Measured Limit Clause
Warning 2 00:00:05.000 00:00:07.000 210 wpm 180 wpm Ofcom: Guidelines on the provision of television access services — Reading speed: subtitles should not exceed 160–180 words per minuteThe first cue is six words in two seconds — 180 words per minute exactly — and it is not reported. The second is seven words in the same two seconds, 210, and it is. Ofcom's sentence is "should not exceed", so the boundary is the limit itself and the comparison is strictly greater. Had this page been written with "at least" instead, the first cue would be in the report and every file would gain findings from cues that were already inside the guidance.
A file whose text has no spaces between words
Subtitles
1
00:00:01,000 --> 00:00:02,000
你好，我一直在等你回来。
2
00:00:03,000 --> 00:00:05,000
我以为你今天不会来了。
What the report finds
Cues read faster than the limit — Not applicable. No per-minute rate can be measured here: either the file holds no words at all, or its text is written without spaces between words (Chinese, Japanese), where counting words by whitespace counts the wrong thing. A characters-per-second standard measures a file like this one.A word-per-minute rate is measured by counting whitespace, and Chinese and Japanese are written without it. One line of Chinese would count as one or two "words", the resulting rate would look extremely slow, and the report would come back clean — a clean report that means nothing. So this page says it cannot measure instead, and points at the check that can: Netflix's characters-per-second limit counts characters, which does not depend on spaces. That is a reason to change document rather than a reason to give up, and the note is in the report so you do not have to guess which of the two you are looking at.
Frequently asked questions
Which Ofcom figures does this page check a subtitle file against?
One. Ofcom's guidelines on the provision of television access services state a reading speed: subtitles should not exceed 160 to 180 words per minute, and this page compares against the upper end of that range, 180. There is no line length, no minimum cue duration and no maximum cue duration anywhere in the document, so three of the five sections of the report say no limit was given. This is not a shortcoming of the page; it is what the document contains, and finding it out is the reason to run the check.
Why do three sections of the Ofcom report say no limit rather than reporting nothing found?
"Nothing found" and "nothing to compare against" are different answers and the report keeps them apart. Nothing found would mean the file was measured against a limit and stayed inside it. What actually happened with line length, minimum duration and maximum duration is that Ofcom states no figure for any of them, so there was no measuring to do. Printing zero findings for those three would make this report look like the Netflix one with empty tables, and would tell you the opposite of the truth about what the guidance covers.
Ofcom states its reading speed in words per minute — is that the same measure as characters per second?
No, and this page does not convert between them. Netflix's limit counts characters; Ofcom's counts words separated by whitespace. Converting one into the other requires assuming an average word length, and the resulting figure would be a number neither document states. So the report measures in words per minute when Ofcom is the document and in characters per second when Netflix is, and each finding quotes the sentence it came from. A file can pass one and fail the other, which is the useful thing to know.
Does Ofcom's guidance require subtitles to identify who is speaking?
Not in the document this page applies. Its speaker section reads that the document says nothing about this, so there is no requirement to check against — a different sentence from the one the three numeric sections print, because the reason is different. Identifying speakers is stated as a duty by WCAG 2.2 Success Criterion 1.2.2 and by the FCC caption quality rules, and both are checked on their own pages. If your compliance obligation comes from either of those, the Ofcom page is not the one that answers it.
What does Ofcom guidance say about a cue that is on screen for less than a second?
Nothing. Neither a minimum nor a maximum cue duration appears in the document, so both duration sections of this report say no limit was given. The one-second figure that circulates in subtitle practice, and the 834 milliseconds the Netflix guide states, come from other documents. A cue of 600 milliseconds on this page is not a finding; the same cue on the Netflix page is.
Is 180 words per minute a legal limit in the United Kingdom?
It is guidance, and the report labels it as such in the row that says how the sentence is stated. Ofcom's access services code sets the obligations on broadcasters and on-demand providers; this figure is in the guidelines that accompany it, written as guidance for people producing subtitles. That distinction is printed on every finding rather than left to the reader, because a number presented as a legal threshold would be a claim this page cannot support.
What the check looks for
- The report describes a file, not a service. Ofcom's access services code and the guidelines this page applies bind television and on-demand providers in the United Kingdom; a subtitle file on its own is not what is regulated. Nothing here concludes that anything complies. What the report states is how many cues measured the way this page measures them, which sentence each figure was read from, whether that sentence is a requirement or guidance, and the day the sentence was last verified against the published document.
- Where the guidance is silent, this page says so in the report rather than filling the gap. Three of the five checks print that no limit was given and one prints that no requirement was stated, because that is the literal state of the document. Anyone who needs a line length or a minimum duration to point at will not find it here, and that is the honest outcome: the alternative would be to borrow another document's number and file it under Ofcom's name.
References
- Ofcom: Guidelines on the provision of television access services — reading speed, subtitles should not exceed 160–180 words per minute. This is the single figure this page applies, and it is guidance rather than a clause of the access services code.
- Ofcom access services code — the obligations on television and on-demand providers in the United Kingdom. Referred to here only to be clear about the boundary: this page applies the guidelines, not the code, and the code is not what a subtitle file is measured against.