Check subtitles for reading speed and line length

What gets checked

• Line length. The longest line in the cue, in characters, against your limit. Formatting tags are not counted.
• Lines per cue. More than two lines (or the number you set) covers too much of the picture.
• Reading speed. Characters per second for the whole cue. This is the check that matters most to viewers: a short cue with a long sentence is gone before it can be read.
• Time on screen. Too short and the cue flashes past; too long and it lingers after the line has been said.
• Overlap and order. A cue that starts before the previous one ends, or before it starts, is reported as an error because players handle it inconsistently.
• Gap. Optional: the quiet time between one cue and the next. Some delivery specifications ask for a minimum gap; if yours does, enter it in milliseconds.

An example

2
00:00:01,000 --> 00:00:02,000
Welcome back to the channel, today we are going to look at how subtitles are timed.

That cue has 83 characters in a single line over one second. Against the Netflix adult preset it fails twice: the line is longer than 42 characters, and it needs 83 characters per second where 20 is the limit. The fix is not to speed up the viewer: split the sentence over several cues with the line splitter and give them more time, which is a decision the checker can point to but cannot make for you.

Why the limits are editable

There is no single correct set of numbers. The two presets use the figures from the Netflix English style guide, which is the most widely quoted one, but a broadcaster, a streaming service in another language or a children's channel each has its own, and languages that need more characters to say the same thing are held to different limits. Choose “My own limits” or edit any box and the preset switches to custom. Set a limit to 0 to turn that check off.

Reading speed on generated subtitles

Subtitles made from a transcript tend to fail on reading speed first, because a speaker who talks at a normal pace says more characters per second than a viewer can comfortably read. That is expected, and it is why professional subtitling condenses speech rather than copying it. For a transcript you made with Scriptorium, run the SRT through this checker, split the long cues, and trim the lines the report flags. transcript file formats explained covers the format itself.

Copying the report

Under the table is the same report as plain text, one line per problem with the cue number and its time, ready to paste into a message to whoever has to fix it.