FREE TOOL · SUBTITLES
Subtitle reading speed checker, line by line
Drop an SRT or VTT file into this subtitle reading speed checker to see characters per second, words per second and on-screen time for every line, with the lines that flash by too briefly or read too fast highlighted. Everything runs in your browser.
- 1
Open the subtitle file
Drop an .srt or .vtt file or paste the text. Formatting tags are ignored when counting characters.
- 2
Choose a reading-speed limit
17 characters per second is a common limit for general audiences; 20 suits fast-paced short-form video where viewers expect dense captions.
- 3
Fix the highlighted lines
Lines under 0.7 second are too brief to read; lines over the limit need fewer words or more time. Merge, split or retime them, then check again.
Why reading speed matters more on short-form video
Viewers of a vertical clip read captions while the picture moves, often with the sound off. A line that stays on screen for less than about seven tenths of a second is gone before the eye reaches it, and a long line squeezed into a short time forces a pause that the scroll does not allow. Reading speed, measured in characters per second, is the simplest way to catch both problems before publishing.
ClipFlap applies the same rule when it renders captions: a word group that would flash for less than 0.7 second is merged with the next one. This checker lets you hold any subtitle file to that standard, whatever tool produced it.
Reading speed questions
What is a good subtitle reading speed?+
Many broadcasters and streaming guidelines cap adult subtitles around 17 characters per second, and some allow up to 20. Children's content and dense technical text usually need less. Short-form captions with two to five words per line often sit well below the limit.
Are spaces counted as characters?+
Yes. Reading-speed guidelines count spaces and punctuation because the eye travels over them; formatting tags such as italics are not counted.
Why is a line under 0.7 second flagged even if it is short?+
Below that duration most viewers cannot read even one word comfortably while watching. Merging it with the line before or after usually fixes it without changing the text.
Does the checker change my file?+
No. It only measures and highlights; your file is not modified or uploaded. Use the subtitle sync fixer if the timing itself needs to move.
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Captions that stay readable
ClipFlap groups words into readable lines and never shows one for less than 0.7 second.