Check captions for Premiere Pro and broadcast specs — characters per line, lines per cue, reading speed (CPS) and cue duration.
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Paste or load an SRT/VTT file to check it against the caption spec.
CPS — characters per second — is how fast a viewer has to read a caption: the number of characters in the cue divided by how long it stays on screen. A cue that holds 80 characters for two seconds runs at 40 CPS, far faster than most people can read. Premiere Pro, Netflix, the BBC and broadcast captioners all cap reading speed (and characters per line, lines per cue and how long a cue may sit on screen) so subtitles are comfortable to read rather than a race.
Typical limits: Netflix 42 characters/line, ≤2 lines, ~17 CPS for adult programs (20 ceiling); BBC 37 characters/line; CEA-608 / US broadcast 32 characters/line. Cues usually stay on screen for at least ~0.8 s (about 20 frames) and no more than ~7 s, with a small gap between cues so they don't flicker. Switch the spec above to check your file against the standard you're delivering to.
This tool is a checker — it reports the cues that break the rules but never rewrites your file. To shift or stretch timing, use the Subtitle Resync tool; to fix cue numbering, overlaps or malformed structure, use the SRT Validator.
Note: character counts use the browser's string length, so most emoji and some double-width (CJK) characters count as two. Treat counts that sit right on the limit as approximate.
A caption file can be perfectly valid — every cue numbered, every timestamp well formed — and still be a poor subtitle track because the lines are too long or the text flies by too fast to read. This checker looks at the part a structural validator ignores: readability and broadcast compliance. It measures characters per line, lines per cue, reading speed (CPS) and how long each cue is on screen, then flags the specific cues that break the spec you are delivering to — the same checks Premiere Pro and broadcast captioners run before sign-off.
CPS — characters per second — is how fast a viewer has to read a caption: the number of characters in the cue divided by the seconds it stays on screen. Eighty characters held for two seconds is 40 CPS, far faster than most people read comfortably. Because reading speed depends on both the text length and the cue duration, two cues with identical wording can pass or fail depending only on their timing — which is why a structural check can't catch it and a reading-speed check can.
Different deliverables enforce different numbers. These are the common house limits this tool ships as presets (max on-screen duration is roughly 7 seconds across the board):
| Spec | Chars / line | Lines / cue | Reading speed | Min duration |
|---|---|---|---|---|
| Netflix | 42 | 2 | ~17 CPS (20 ceiling) | ~0.83 s |
| BBC | 37 | 2 | ~15–18 CPS | ~0.83 s |
| CEA-608 / US broadcast | 32 | 2 | ~15–17 CPS | ~1 s |
| Premiere (generic) | 42 | 2 | ~16–20 CPS | ~1 s |
Switch the preset to match your client, or choose Custom and type your own limits.
This is a checker, not a fixer, and it is deliberately scoped to readability. It does not renumber cues, repair overlaps or correct malformed timestamps — that is structural validation, and a dedicated SRT validator owns it. It also does not shift or stretch your timing; a resync tool owns that. Keeping the jobs separate means each report is clear about what actually needs fixing.
Premiere Pro shows captions as a caption track and can warn on reading speed, but it won't give you a tidy, cue-by-cue compliance list to hand a client or QA against a delivery spec. Paste your exported subtitles here to get that list before you publish — or to sanity-check a file someone else captioned. Everything runs locally in your browser; nothing is uploaded.
CPS stands for characters per second — the caption's character count divided by how many seconds it stays on screen. It is the standard measure of subtitle reading speed. Most adult specs target around 15–17 CPS and treat 20 CPS as a hard ceiling; above that, viewers can't finish reading before the cue disappears.
The common subtitle character limit is 42 characters per line (Netflix and many streaming specs), 37 for the BBC, and 32 for CEA-608 / US broadcast captions. Almost every spec also limits a cue to two lines. This checker measures your longest line per cue and flags any that exceed the limit you select.
Netflix's timed-text style guide caps lines at 42 characters, allows a maximum of 2 lines per cue, and sets reading speed at 17 CPS for adult programs (with 20 as the ceiling). Cues should stay on screen for at least about 0.83 seconds (20 frames) and no longer than ~7 seconds. Select the Netflix preset above to check against these numbers.
Long enough to read and no longer. Most specs use a minimum of ~0.83–1 second (around 20 frames) so a cue doesn't just flash, and a maximum of ~7 seconds so a single subtitle doesn't linger. Just as important is reading speed: a short cue packed with text still fails if its CPS is too high. The checker reports both the duration and the CPS for every cue.
Premiere Pro warns when a caption exceeds its reading-speed or length settings — usually because a line is over the character limit, a cue has too many lines, or the text is on screen too briefly for its length (high CPS). This tool shows you exactly which cues trip those rules and by how much, so you can adjust the wording or timing before exporting.
No. It is a checker — it reads your file in the browser and reports the cues that break the spec, but it never rewrites or downloads a modified file. To shift or stretch the timing, use a subtitle resync tool; to fix cue numbering, overlaps or malformed structure, use an SRT validator.
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