WebVTT Caption Validator
Paste a WebVTT caption file and validate its structure, timing, and coverage of the source media.
Editorial guidance
How this media tool supports accessibility work
The video caption (webvtt) validator is designed to turn a common accessibility review task into a repeatable workflow. It focuses on parses webvtt files and validates cue structure, timing, and coverage. The goal is not to replace expert judgment, but to make the first review faster, more consistent, and easier to explain to designers, developers, QA teams, and content owners.
Use the output as evidence for a remediation conversation. A failed check normally means the implementation needs a closer look against WCAG 1.2.2, 1.2.4, while a passing check means the specific automated rule did not find a problem. Passing automated checks is helpful, but it is not the same as a full conformance claim.
For best results, test real production markup instead of simplified snippets. Templates, CSS state, JavaScript behavior, responsive layouts, and content changes can all affect the final accessibility experience. Re-run the tool after fixes so the before-and-after evidence is easy to compare.
Pair this tool with manual keyboard testing, zoom and reflow checks, screen-reader review, and content judgment. Those human checks catch issues that automated logic cannot reliably infer, such as whether labels are meaningful, instructions are clear, or a complete user task can be finished without a mouse.
How to use
- 1Paste your WebVTT file contents into the validator.
- 2Check the output for syntax issues, cue timing problems, overlaps, or poor coverage gaps.
- 3Fix the caption file and re-run it before publishing so players and users get more reliable playback support.
FAQs
Tips here are tailored for the video caption (webvtt) validator so people can move from checking to fixing faster.
What to verify manually
Keyboard: move through the related flow with Tab, Shift+Tab, Enter, Space, Escape, and arrow keys where the pattern expects them.
Assistive technology: check names, roles, states, reading order, announcements, and focus changes with at least one screen reader.
Content quality: confirm that instructions, labels, headings, errors, and alternatives make sense in the real user task.
This page is written as practical guidance, not a legal certification. For procurement, VPAT/ACR work, or regulated launches, combine tool output with expert review and documented manual test results.
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