YouTube Subtitle Checker and Converter: SRT, VTT and SBV
Check SRT, VTT and SBV captions for timing and format problems, convert them and shift their times.
- Free to use
- Runs in your browser
- No sign-up
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About the YouTube Subtitle Checker and Converter
Paste your captions or open an .srt, .vtt or .sbv file. The tool finds the format, reads every cue and checks the timings, time order, overlaps, empty cues, style markup and text encoding against YouTube Help and the WebVTT rules, plus our readability checklist. Then convert the captions to SRT, WebVTT or SBV, shift the times earlier or later, and download a UTF-8 file. It all runs in your browser.
How it works
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Step 1
Paste the captions, open the caption file, or click "Try an example".
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Step 2
Read the checks and the cue table, and fix what is flagged in your caption file or editor.
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Step 3
Choose SRT, WebVTT or SBV, shift the times if the captions run early or late, and download or copy the file.
Formats YouTube accepts
YouTube Help lists basic formats such as SubRip (.srt) and SubViewer (.sbv or .sub), and advanced ones such as WebVTT (.vtt), which supports positioning, with styling limited to <b>, <i> and <u>. For SRT and SBV, only basic files are supported: no style markup is recognised, and the file must be plain UTF-8. YouTube suggests SRT or SBV for beginners, as you can edit them in a plain text editor.
What the checks look at
Under the W3C WebVTT rules, a WebVTT file starts with WEBVTT, and each time has optional hours, two-digit minutes and seconds, a full stop and three digits of milliseconds. SRT and SBV have no official specification, so their times are checked against the usual layout. Line length (42 characters), lines per cue (2) and reading speed (about 20 characters a second) are our checklist, not YouTube rules.
What this tool cannot do
It checks the file, not the words: it cannot hear your video, so it cannot tell whether the captions match what is said or whether they are in sync. It reads SRT, WebVTT and SBV only, not the other formats YouTube accepts, such as SCC or TTML. It does not upload anything to YouTube.
Frequently asked questions
Which subtitle file format is best for YouTube?
YouTube Help suggests SRT or SBV for beginners, because they are plain text. Use WebVTT if you need bold, italics, underline or positioning, which YouTube supports in WebVTT files. Whichever you choose, save the file as UTF-8. This tool converts between the three.
How do I convert SRT to VTT?
Paste the SRT or open the file, choose WebVTT and download. The tool adds the WEBVTT header, writes each time with a full stop before the milliseconds, keeps <b>, <i> and <u> tags and removes other markup. It converts the other way too, from WebVTT or SBV to SRT.
My captions are out of sync. How do I fix the timing?
If every caption is early or late by the same amount, enter the difference in seconds in "Shift times": minus moves them earlier, plus moves them later. If only part of the video is off, for example after a cut, enter the first cue to move in "From cue". Then download the corrected file.
Why do my subtitles show strange characters?
A common cause is a file that was not saved as UTF-8; YouTube Help says SRT and SBV files must be plain UTF-8. Characters that could not be read show as � here, and text saved in the wrong encoding often looks like é or à¤. Save the original as UTF-8 in your text editor and check it again.
How long should a subtitle line be?
YouTube does not publish a limit. Our checklist uses up to 42 characters a line, at most 2 lines a cue and about 20 characters a second, so viewers can read each caption before it goes. Treat them as guides: a fast conversation may need shorter cues rather than longer lines.
Sources and checks
Rules last checked
The YouTube Subtitle Checker and Converter follows these official pages:
- Supported subtitle and closed caption files (support.google.com)
- WebVTT: The Web Video Text Tracks Format (w3.org)
SRT and SBV have no official specification, and the line length and reading speed checks are our checklist.
Scores, limits and suggestions marked "our checklist", "our measure" or "our suggestion" are ours, not Google's or the platform's. How our tools work
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