SRT Validator

Why a player refuses to load your subtitles

SubRip is unforgiving about small things. A period instead of a comma in the milliseconds, a missing sequence number, a stray blank line — and the player either skips part of the file or shows nothing at all. It almost never tells you why: the subtitles simply do not appear.

This validator walks the file block by block and tells you what is wrong and exactly where. The check runs in your browser; the file is never uploaded.

What gets checked

Flagged as errors: a block with fewer than two lines, a missing or unreadable sequence number, a missing or unparseable timecode line, and an end time that is not after the start time. Flagged as warnings: a sequence number out of order, a timecode that is not in hh:mm:ss,mmm form, an overlap with the previous cue, empty subtitle text, and a cue that stays on screen longer than 15 seconds.

The split matters. An error usually means the file will not load or will silently lose blocks. A warning means the file works but a viewer will notice something is off — a subtitle hanging too long, or two cues stacking on top of each other.

What to do with the report

Small fixes are easiest by hand: the report gives you block numbers, and an .srt opens in any text editor. If overlaps run through the whole file, rebuilding it is usually faster than patching cue by cue.

If the structure checks out but the subtitles still drift against the speech, the format is not the problem — use the time shift tool, which moves every timecode at once. And if the file was assembled from several parts, look at the joins first: that is where overlaps normally appear.

How fast can subtitles be read?

For English adult programs, the Netflix Timed Text Style Guide allows up to 20 characters per second and 42 characters per line, and for children's programs up to 17 characters per second. The BBC Subtitle Guidelines state the same limit in words, 160 to 180 words per minute, while the DCMP Captioning Key, written for educational media, asks for no more than 130 words per minute at lower level and 160 at upper level.

The reading-speed check above measures your file against whichever guide you pick. It runs separately from the format check: a file can be perfectly valid SRT and still flash a long sentence past faster than anyone can read it.

How the check counts

Characters per second is the length of a cue's text divided by its time on screen. The validator removes markup such as <i> and {\an8}, counts spaces and punctuation, and does not count the line break. For the BBC and DCMP guides it counts words instead, because that is how those guides state their limit, and it checks only the limits each guide actually sets.

What our own auto-timing produces

We ran the Gettysburg Address, split into its ten paragraphs, through our TXT to SRT tool, which times text at 150 words per minute and holds every cue between 2 and 8 seconds. The two short paragraphs, 10 and 11 words, came out at 11.8 and 13.4 characters per second, comfortably inside the Netflix adult limit. Every paragraph longer than 20 words hit the 8-second cap, which is already over the 7-second Netflix maximum and the 6-second DCMP maximum, and the closing 86-word paragraph landed at 56.0 characters per second, nearly three times the limit. Split long paragraphs into short lines before generating, then run the result through this check.