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Caption / SRT Validator

Check subtitle timing and formatting.

100% FreeRuns instantlyNo watermark
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  1. 1Choose toolOpen the Vootkit workspace.
  2. 2Add inputProvide the content or settings.
  3. 3ProcessLet the browser do the work.
Private by designProcessed on your device where possible.
Works on any deviceDesktop, tablet and mobile browsers.
No installationOpen the page and start working.
Always free coreUse the free plan for everyday tasks.

How to use Caption / SRT Validator

Choose tool

Open the Vootkit workspace.

01
Add input

Provide the content or settings.

02
Process

Let the browser do the work.

03
Finish

Copy, download or continue.

04

Your files stay private

Your work is processed locally in your browser where possible and is never added to a Vootkit upload library.

Learn more about privacy
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A caption file that is a fraction of a second out is worse than no captions, because the words on screen belong to a sentence that has already finished — and a malformed timestamp can stop the whole file loading.

What Caption / SRT Validator does

Checks SRT and VTT caption files for structural problems: malformed timestamps, out-of-order entries and overlaps.

The two formats look similar and differ in ways that break silently — SRT uses a comma before milliseconds, VTT uses a full stop, and VTT requires a WEBVTT header line.

The two formats

SRT timestamp<code>00:00:01,500</code> — <strong>comma</strong>
VTT timestamp<code>00:00:01.500</code> — <strong>full stop</strong>
VTT requiresA <code>WEBVTT</code> first line
ChecksMalformed timestamps, ordering, overlaps
Reading speedAround 160–180 words per minute is comfortable
Line lengthTwo lines of ~32 characters is the usual limit
<strong>Cannot check</strong><strong>Whether the text matches the audio</strong>
RunsOn your device

Detailed steps

  1. Paste the caption file.
  2. Fix timestamp and ordering errors.
  3. Watch the video with the captions on — that is the only real test.

Worth knowing

The comma-versus-full-stop difference between SRT and VTT is the single commonest cause of a caption file that will not load. Renaming a .srt to .vtt does not convert it: the timestamps still use commas, and the player rejects the file with an error that rarely says why. Convert properly, and add the WEBVTT header.

Frequently Asked Questions

What is the difference between SRT and VTT?

VTT is the web standard and supports styling and positioning; SRT is older and plainer. Structurally the differences that break things are the millisecond separator — comma in SRT, full stop in VTT — and VTT’s required WEBVTT header.

My captions will not load.

Check the separator first. A file renamed from .srt to .vtt keeps comma timestamps and will be rejected. Then check for a WEBVTT header, and for a stray blank line inside a cue.

How fast should captions go?

Around 160–180 words per minute is comfortable to read. Faster than that and viewers miss text; the usual convention is two lines of roughly 32 characters per cue.

Does valid mean accurate?

No. It means the file is well-formed. Whether the words match what is said, and whether the timing feels right, can only be judged by watching the video with them on.

Is Caption / SRT Validator free?

Yes. The Vootkit free plan includes 5 tool runs a day. Upgrade to Vootkit Pro for unlimited daily use, an ad-free workspace and saved workflows.

Are my files uploaded?

No. Caption / SRT Validator runs entirely in your browser — your file is processed on your own device and never sent to a server. There is nothing for us to store or delete.

Do I need to install anything?

No. Caption / SRT Validator works in any modern browser on desktop, tablet or phone. Open the page and start.

How often can I use it? Is there a daily limit?

On the free plan you get 5 tool runs a day. When you reach the limit you'll see a prompt to upgrade, and it resets the next day. Vootkit Pro removes the cap entirely for unlimited daily use.

This tool processes everything locally in your browser. You can disconnect from the internet after the page loads and it will still work.