What is CPS?Characters per second — how much text a viewer must read for every second a caption is on screen, counting spaces. Netflix caps adult content at ~17 CPS; short-form viewers reading on small screens while half-distracted need slower.
Why it kills retentionWhen a caption disappears mid-read, the viewer's brain registers a tiny failure. A few of those and the swipe-away is reflexive. Pacing problems hide in analytics as a "weak hook" when the real issue is unreadable text.
How to fix a fast cueThree options, in order: extend the cue into the silent gap that follows it, split one long cue into two shorter ones, or trim words. The report suggests which applies to each flagged cue.
Why caption reading speed matters for Shorts, Reels and TikTok
Most short-form videos today are watched with captions on — often with sound off. Every caption has a hidden deadline: the moment it leaves the screen. If the text demands a reading speed faster than your viewer can manage, they miss words, lose the thread, and swipe away. Because nothing "looks" broken in the editor, this problem almost never gets caught. Analytics will blame your hook or your topic, when the real issue was a two-second caption carrying a four-second sentence.
The Caption Speed Checker measures every cue in your subtitle file in characters per second (CPS) — the same readability metric used by Netflix, the BBC and professional subtitlers — and flags everything above a comfortable threshold. For short-form content viewed on phones, we recommend staying at or below 13 CPS, with anything above 17 CPS treated as unreadable for most viewers. You also get word-per-minute figures, minimum on-screen duration checks, line-length warnings, and overlap detection.
Unlike generic subtitle editors, this tool tells you how to fix each flagged caption: it checks the silent gap after every fast cue and calculates whether extending the cue is possible — and by exactly how many seconds — before suggesting a split or a trim. Use the playback preview to feel the pacing yourself, then export the full report as CSV or copy problem timestamps straight into your editing notes.
Frequently Asked Questions
What is CPS (characters per second) in captions? ›
CPS measures how much text a viewer must read for every second a caption is on screen, counting spaces. Broadcast and streaming standards like Netflix cap adult subtitles around 17 CPS. Short-form viewers reading on small screens need slower — around 13 CPS is comfortable.
What caption speed is best for Shorts, Reels and TikTok? ›
Aim for 13 CPS or below for comfortable reading. Between 13 and 17 CPS is borderline. Above 17 CPS most viewers cannot finish reading the caption before it disappears, which silently hurts retention.
Which subtitle formats does the Caption Speed Checker support? ›
It supports SRT and VTT (WebVTT) files exported from YouTube Studio, Premiere Pro, CapCut, DaVinci Resolve, Descript and most other editors. You can also paste subtitle text directly.
Is my subtitle file uploaded to a server? ›
No. The entire analysis runs locally in your browser using JavaScript. Your file is never uploaded, stored, or sent anywhere — close the tab and it's gone.
How do I fix a caption that is too fast? ›
Three fixes in order of preference: extend the cue into the silent gap that follows it, split one long cue into two shorter ones, or trim filler words. The report tells you which fix applies to each flagged caption, including exactly how many seconds to extend.
Does it work for Hindi and other non-English captions? ›
Yes — it parses and times captions in any language. The CPS thresholds are calibrated for Latin scripts; for dense scripts like Devanagari or CJK, treat the thresholds as slightly conservative and rely on the real-time playback preview to judge readability.