JSON Formatter
Free JSON formatter and validator. Beautify or minify JSON, sort keys, explore a tree view and find errors by line and column. Runs privately in your browser.
- No upload — 100% private
- Instant, on your device
- Free, no sign-up
- Works offline once loaded
How it works
How to use JSON Formatter
Paste JSON, open a .json file or load the sample.
Choose Beautify (2 spaces, 4 spaces or tabs) or Minify, and optionally sort keys A→Z.
If the JSON is invalid, read the exact line, column and reason, then jump straight to the error.
Switch to Tree view to collapse and explore nested data, then copy or download the result.
Why use it
Why use our JSON Formatter tool
Precise error messages
Pinpoints the line and column of trailing commas, single quotes, missing commas and unquoted keys.
Beautify or minify
Pretty-print with 2 spaces, 4 spaces or tabs, or strip every byte of whitespace for production.
Collapsible tree view
Expand and collapse objects and arrays with item counts to navigate big API responses quickly.
Sort keys
Recursively sort object keys alphabetically so two JSON documents are easy to compare.
Handles big files
Parsing runs in a background worker, so multi-megabyte JSON never freezes the page.
Private by design
Your JSON never leaves your device — ideal for API keys, tokens and customer data.
FAQ
Frequently asked questions
Why is my JSON invalid?
The most common causes are trailing commas, single-quoted strings, unquoted property names, comments and values like undefined or NaN. The validator names the exact problem and its line and column.
What is the difference between beautify and minify?
Beautify adds indentation and line breaks so humans can read the structure. Minify removes all optional whitespace to make the payload as small as possible for transfer or storage.
Can it format very large JSON files?
Yes. Formatting runs in a Web Worker off the main thread, and the editor only draws the line numbers you can see, so files of several megabytes stay responsive.
Does sorting keys change my data?
No values change — only the order of keys inside objects. Arrays keep their original order because order matters in arrays.
Are very large numbers preserved exactly?
JSON numbers are read as JavaScript doubles, so integers above 2^53 (about 9 quadrillion) may lose precision when reformatted. Store such IDs as strings to keep them exact.
Is it safe to paste sensitive JSON here?
Yes. Everything is processed locally in your browser. Nothing is uploaded, logged or stored on a server.
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