JSON formatter
Parse, validate, and pretty-print JSON with syntax highlighting. Shows exact error location for malformed input. Client-side only.
Client-side only — JSON is parsed locally using the browser's native JSON.parse. Nothing is sent to a server. Syntax highlighting is handled by a custom tokenizer with zero external libraries.
Guide
JSON Formatter: what it does and how to use it
What this Developer tool does
This JSON formatter validates, formats, and helps inspect JSON data. Developers use it to debug API responses, configuration files, webhook payloads, package metadata, and structured logs.
How it works
Paste JSON and the browser parses it locally. Valid input is pretty-printed with consistent indentation, while invalid input returns an error that helps locate syntax issues such as missing commas or unquoted keys.
Examples
- Format an API response before sharing it in documentation.
- Validate a webhook payload.
- Minify or inspect JSON configuration.
Security considerations
JSON can contain tokens or personal data. The formatter runs locally, but you should still avoid pasting sensitive production data on shared machines.
FAQ
Why is my JSON invalid?
Common causes are trailing commas, comments, single quotes, and unescaped characters.
Does this support JSON5?
No. It validates standard JSON.
Is the data uploaded?
No. Formatting happens in your browser.