Caption Speed Checker

What the checker measures

• Characters per second (CPS) — the number of characters in a caption (spaces included, line breaks and tags excluded) divided by how long it is on screen. It is the most common measure of whether viewers have time to read a subtitle.
• Words per minute (WPM) — an alternative reading-speed measure used by some broadcast guidelines.
• Characters per line (CPL) — long lines are hard to read and may be cut off on phones.
• Duration and gaps — very short captions flash past, and overlapping captions (a negative gap) confuse many players.

Which limits should I use?

There is no single universal standard. Many streaming style guides use limits in the region of 15–20 characters per second for adult content and around 37–42 characters per line, with lower speeds for children's content. Broadcasters' guidelines — for example the BBC's published subtitle guidelines — are often expressed in words per minute instead. The defaults above (17 CPS, 42 CPL, 1 second minimum) are a sensible middle ground for online video; tighten them for younger audiences or dense technical content. Our guide to caption reading speed explains the trade-offs, and short-form captions covers the very different style used on Shorts and Reels.

How to fix a caption that is too fast

1. Extend it into a following gap if the audio allows.
2. Split it into two captions at a natural pause.
3. Edit the wording — remove filler words and repetition while keeping the meaning.

If every caption is slightly off, the whole file may need re-timing — try the SRT Shifter.

FAQ

Why are some rows highlighted?

Red rows break your CPS limit or overlap the next caption. Amber rows have a line that is too long or a duration shorter than your minimum.

Are formatting tags counted?

No. Tags such as <i> and {\an8} are removed before counting, because viewers never see them.

Is my file stored?

No. Everything happens in your browser and nothing is sent to a server.