Convert JSON to VTT Online Free
Transform JSON subtitle or transcript data into WebVTT format for HTML5 video players, accessibility tools, and streaming platforms. Perfect for developers building video pipelines.
By ChangeThisFile Team · Last updated: March 2026
ChangeThisFile converts JSON subtitle data to WebVTT format on a secure server. Upload your JSON transcript file and it is converted to a valid VTT file compatible with HTML5 video players. Files are auto-deleted after conversion. Free with no signup required.
Convert JSON to VTT
Drop your JSON file here to convert it instantly
Drag & drop your .json file here, or click to browse
Convert to VTT instantly
JSON vs VTT: Format Comparison
Key differences between the two formats
| Feature | JSON | VTT |
|---|---|---|
| Purpose | General-purpose data exchange | Timed text tracks for web video |
| Format | Key-value pairs and arrays | Timed cue blocks with timestamps |
| Browser support | Parsed with JavaScript | Native HTML5 <track> element support |
| Timestamp format | Flexible (ms, seconds, ISO) | HH:MM:SS.mmm --> HH:MM:SS.mmm |
| Styling | No built-in support | CSS ::cue pseudo-element styling |
| Accessibility | Not directly usable for captions | Standard for web accessibility captions |
| Use with video players | Requires custom parsing | Supported by all HTML5 players natively |
When to Convert
Common scenarios where this conversion is useful
Video pipeline subtitle generation
Convert JSON transcript data from speech-to-text APIs (like AWS Transcribe or AssemblyAI) to VTT for attaching captions to HTML5 video players in web applications.
Accessibility compliance for web video
Transform JSON caption data to WebVTT for adding accessibility-compliant captions to HTML5 video elements, meeting WCAG 2.1 and ADA requirements for web content.
Streaming platform subtitle delivery
Convert JSON subtitle exports from editing tools or transcription services to VTT for upload to streaming platforms, learning management systems, or video CDNs.
E-learning and training video captions
Transform JSON transcripts from recorded training sessions or course videos to VTT for adding searchable, accessible captions to e-learning platforms.
How to Convert JSON to VTT
-
1
Upload your JSON file
Drag and drop your JSON subtitle or transcript file onto the converter, or click browse to choose from your device. The file is sent over an encrypted connection.
-
2
Server-side conversion
The server parses your JSON data and converts it to WebVTT format. Cue entries are produced from the JSON timestamps and text fields, following the WebVTT specification.
-
3
Download the VTT file
Save your converted .vtt file. The server copy is automatically deleted after processing. Use the VTT file directly with HTML5 <track> elements or video players.
Frequently Asked Questions
The converter expects a JSON array of objects with start, end, and text fields (or similar timestamp and content properties). Common formats from AWS Transcribe, AssemblyAI, and similar APIs are supported.
Timestamps in milliseconds (numbers), seconds as floats, and ISO 8601 duration strings are all supported. The converter normalizes them to the VTT HH:MM:SS.mmm format automatically.
Yes. The converter produces valid WebVTT output that starts with the required WEBVTT header, uses correct cue block formatting, and follows the W3C WebVTT specification.
Yes. The resulting .vtt file works directly with the HTML5 <track> element. Add it to your video with <track kind='captions' src='subtitles.vtt' srclang='en'>.
The converter produces standard timed cues. Advanced VTT features like cue settings (position, align, line) require editing the output file after conversion.
Yes. Uploads use HTTPS encryption. Files are deleted from the server immediately after conversion. No data is retained.
Yes, completely free. No account, no credit card, no conversion limits.
Yes. AWS Transcribe outputs JSON with transcript items and timestamps. The converter maps these to VTT cue blocks. You may need to consolidate word-level items into phrase-level cues first.
WebVTT (Web Video Text Tracks) is the W3C standard format for displaying timed text tracks in HTML5 videos. It is supported natively by all modern browsers and is the preferred format for web accessibility captions.
Yes. ChangeThisFile supports VTT to JSON conversion as well, so you can convert in both directions for round-trip workflows.
Related Conversions
Related Tools
Free tools to edit, optimize, and manage your files.
Need to convert programmatically?
Use the ChangeThisFile API to convert JSON to VTT in your app. No rate limits, up to 500MB files, simple REST endpoint.
Ready to convert your file?
Convert JSON to VTT instantly — free, no signup required.
Start Converting