JSON Formatter & Validator
Beautify, minify and validate JSON instantly. Errors are pinpointed by line and column. 100% local - nothing leaves your browser.
Processed locally with your browser's native JSON engine. Files you open or drop are read in your browser only - we never receive, upload or store them. No network requests, no tracking.
About
This tool beautifies, minifies and validates JSON straight in your browser. Paste or drop a file and it pinpoints syntax errors by exact line and column, offers one-click auto-fix for common issues like trailing commas or missing quotes, and lets you switch between raw text and a collapsible tree view for deeply nested data.
Everything runs 100% client-side - your JSON is parsed locally and never uploaded or sent to a server, which makes it safe to use with API keys, tokens or other sensitive payloads.
Frequently Asked Questions
About the JSON Formatter & Validator.
No. This JSON formatter runs entirely in your browser using native JavaScript. Your JSON never leaves your machine - there are no network requests, no logging, and no storage. This makes it safe to paste API responses, tokens, or any sensitive payload.
Beautify pretty-prints your JSON with consistent indentation (2 or 4 spaces) and line breaks so it is easy to read and diff. Minify strips all unnecessary whitespace to produce the most compact valid JSON, which is ideal for reducing payload size in requests and config files.
When parsing fails, the tool reports the exact line and column of the problem plus a human-readable explanation - for example a trailing comma, a missing comma between values, single quotes instead of double quotes, or an unclosed bracket. This is far more useful than the terse default message browsers produce.
The JSON specification does not allow a comma after the last element of an object or array (unlike JavaScript object literals). The validator points at the offending comma so you can remove it. The same applies to comments - standard JSON does not support // or /* */ comments.
Yes. Formatting is debounced and uses the browser's native, highly optimized JSON engine, so even multi-megabyte inputs format near-instantly without locking up the UI.
Yes. One click copies the formatted or minified output to your clipboard. You can also clear the editor instantly to start over.
From the blog
How to Fix a Broken JSON File: The Developer's Guide to Syntax Errors
A practical guide to diagnosing and fixing common JSON syntax anomalies like trailing commas, unexpected tokens, and BOM issues.
Read →jsonJSON vs. JSONC vs. JSON5: Why Your Config File is Breaking the API
Understand the structural differences between JSON, JSONC, and JSON5 to stop syntax errors and choose the right format for your project.
Read →