What the Subtitle Line Break Formatter does
This formatter re-breaks the text of every subtitle into one or two balanced lines within a character limit you choose, following the line-break conventions in the Netflix and BBC style guides: break after punctuation or before a conjunction or preposition, never leave an article, preposition or pronoun dangling at the end of a line, and keep first and last names together. Timecodes are never touched.
It is for the tidy-up step after automatic transcription or a hurried edit, when cues arrive as one long line or with a stray word on a line of its own. The result downloads as SRT or WebVTT, and cues that cannot fit at all are listed rather than squeezed.
How to use it
- Paste an SRT or WebVTT file, or drop it onto the box.
- Set characters per line - 42 is the Netflix figure for English, 37 the BBC broadcast figure, and shorter lines suit vertical video - and the maximum number of lines.
- Tick "Only re-break cues that break the limit" if a subtitler has already broken most lines by hand and you only want the problem cues fixed.
- Press Re-break lines. The table shows each changed cue before and after, with every line's character count in brackets.
- Copy or download the file in the same format as the input, or convert between SRT and WebVTT with the output format menu.
Reading the results
Among the breaks that fit, the formatter scores every possible break point and keeps the lowest score. Unequal line lengths add to the score; a break after a full stop, comma or colon lowers it; ending a line on an article, preposition, conjunction, auxiliary verb or subject pronoun adds a large penalty; splitting two capitalised words, a likely name, adds another.
A text that fits on one line stays on one line, because guides prefer a single line when it fits. Two-speaker cues where each line starts with a dash are left exactly as they are, since each line belongs to a different speaker.
Still over the limit means no arrangement of the words fits. That is an editing problem, not a formatting one: shorten the text or split the cue in two with new timing.
Worked example: tidying an auto-generated interview transcript at 42 characters
Load the interview example. Cue 1 arrives as one 82-character line. The only ways to fit it into two lines of 42 are breaks near the middle, and the formatter chooses "When we started the project in 2019 nobody" (42) and "believed the river could be cleaned up." (39).
Cue 2 has the word "and" stranded on a line of its own, making three lines. Joined and re-broken, it becomes "I spoke to Maria Delgado at the council" (39) and "and she said we should just try." (32): the break falls before the conjunction and keeps Maria Delgado together.
Cue 3 already fits on one line and cue 4 is a two-speaker exchange, so both are left alone. Cue 5 has 101 characters, more than the 84 two lines of 42 can hold, so it is listed as still over the limit - it needs condensing or splitting, which only an editor can decide.
Why line breaks matter as much as reading speed
Viewers read a subtitle in one or two glances. A line that ends on "the" or "of" forces the eye to jump to the next line before the phrase makes sense, which slows reading even when the characters-per-second figure is fine. Breaking at natural phrase boundaries keeps each line a meaningful chunk.
Balanced lines also sit better on screen. Most guides accept either a slightly longer top or bottom line; the formatter prefers a bottom-heavy shape only as a tie-breaker, because what the phrase says matters more than the shape.
Limitations: what the result does not prove
- The rules are English-language conventions. Other languages have different words that must not end a line - French and German guides, for example, have their own lists - so check results for non-English text.
- Name detection is a simple capitalisation rule: it will also keep together two capitalised words that are not a name, and it cannot see a name written in lower case.
- It never shortens, rewords or retimes anything. Cues that cannot fit are reported, and reading speed is checked separately by the Subtitle Reading Speed Checker.
- Formatting tags such as <i> are kept and not counted towards line length, but a tag that spans a new line break may need checking in your editor.
Privacy: where your data goes
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Standards and sources
- BBC Subtitle Guidelines - checked 19 Sep 2026
- Netflix English (USA) Timed Text Style Guide - line treatment
- W3C - WebVTT cue settings
Frequently asked questions
How many characters should a subtitle line have?
It depends on the platform and the screen. Netflix's English guide allows 42 characters a line; the BBC uses 37 for broadcast and a percentage of the video width online. Vertical video usually needs shorter lines, around 25-32 characters, because the frame is narrow.
Where should I break a two-line subtitle?
After punctuation where possible, otherwise before a conjunction or preposition. Keep together an article and its noun, an adjective and its noun, a first and last name, and a pronoun and its verb. This formatter applies those rules automatically and shows you the result.
Should a subtitle be one line or two?
If the text fits on one line within the limit, one line is preferred - it is quicker to read and covers less of the picture. Two lines are for text that does not fit, and three are rarely allowed outside specific broadcast or accessibility formats.
Will re-breaking lines change my timecodes?
No. Only the text inside each cue is rearranged; start and end times, the cue order and WebVTT cue settings such as line position are kept exactly. Cues with unreadable timecodes are left out and reported so nothing is silently guessed.
Why are dialogue cues with dashes left alone?
In a two-speaker cue each dashed line belongs to a different speaker, so the break is fixed by who is talking, not by line length. If such a cue is too long, the fix is to trim one speaker's line or split the exchange.
Can it fix a subtitle that is simply too long?
No, and it will not pretend to. If the words cannot fit in the number of lines you allow, the cue is listed as still over the limit. Condensing dialogue changes meaning, so that stays an editor's decision.
Last reviewed by the A2Z.Tools team against the sources listed above.
