CaptionStack
Private by design

JSON TO VTT

JSON to VTT.

Convert JSON (.json) subtitles to WebVTT (.vtt) in seconds. No upload, no sign-up, nothing leaves your browser.

SRTVTTSBVLRCTTMLJSONCSVTXT
1

Choose your caption file

We’ll detect the format automatically. Drop several files to convert them all at once.

Don’t have a file handy?
2

Choose an output format

Select what you need on the other side.

100% privateYour files never leave this device.
8 formatsBuilt for the caption formats you use.
No limitsConvert as often as you need.

How to convert JSON to VTT

  1. Drop your .json file into the converter above, or click to browse. Several files at once become a ZIP.
  2. Check the quality report and fix timing or text in the editor if you need to.
  3. VTT is already selected as the output format. Click Download converted file.

Conversion happens entirely in your browser. Nothing is uploaded, no account is needed, and there is no file count limit.

About JSON (.json)

JSON is the easiest format to consume from code. CaptionStack reads an array of cue objects or an object with a cues array, accepts timestamps as milliseconds or time strings, and writes a versioned document with millisecond start and end values so you can load captions straight into a web app, database, or analytics pipeline.

About WebVTT (.vtt)

WebVTT is the native caption format for the HTML5 <track> element and for most web players, including Video.js, Plyr, and HLS streams. It looks similar to SRT but requires a WEBVTT header, uses a period before the milliseconds, and supports optional cue identifiers, positioning settings, and styling.

What changes when converting JSON to VTT

Cue identifiers are preserved when the source has them. Positioning and styling settings are not carried from other formats, and VTT NOTE, STYLE, and REGION blocks are skipped on import.

Frequently asked questions

Is this JSON to VTT converter free?
Yes. CaptionStack is free and open source, with no limits on file count or conversions.
Are my caption files uploaded anywhere?
No. Parsing and conversion run in your browser using a local Web Worker. Your files never leave your device.
Can I edit the captions before exporting to VTT?
Yes. After import, open the editor to adjust start and end times, fix text, split, merge, or reorder cues. The quality report flags overlaps, short cues, and fast reading speeds with one-click fixes.
Can I convert many .json files to .vtt at once?
Yes. Drop multiple files and download all of the results as a single ZIP archive.

Other JSON conversions

Other ways to get VTT

All caption formats