What is the largest JSON file this tool can format?

Roughly 10 MB before the browser tab starts to slow down. The formatter uses the browser's native JSON.parse and JSON.stringify, so the practical limit is your device's available memory. All processing runs in your browser.

What happens if my JSON is invalid?

The tool highlights the error and shows the line and character position of the problem so you can fix it quickly.

Can I format JSON with comments?

Standard JSON does not allow comments. If your input contains them (JSONC format), the tool will flag them as invalid. Remove comments before formatting.

Is there a size limit?

There is no hard limit. The tool processes JSON entirely in browser memory. Very large files (over 10 MB) may be slow.

JSON Formatter

JSON formatter is a developer tool that pretty-prints, minifies, and validates JSON. It supports custom indentation, sorts keys alphabetically, and reports parse errors with line numbers. The tool runs in your browser.

Input JSON

Output

FORMAT

Tips

Paste JSON in the left pane. Output updates instantly.

Runs entirely in your browser

Dedicated pages

Direct links for each JSON operation.

JSON Formatter & Pretty Printer

Format and pretty-print JSON instantly in your browser. All processing runs in your browser.

JSON Minifier

Minify JSON by removing all whitespace in your browser. Useful before embedding in code or sending over a network.

JSON Validator

Validate JSON syntax instantly in your browser. Get clear error messages. All processing runs in your browser.

Sort JSON Keys

Sort all keys in a JSON object alphabetically, recursively. Free, private, runs in your browser.

How to format JSON

Paste your JSON into the input area, minified, pretty-printed, or anything in between.
The formatter validates and pretty-prints your JSON automatically.
Adjust the indent size (2 or 4 spaces) if needed.
Click "Copy" to copy the formatted JSON to your clipboard.

Common uses

Pretty-printing API responses to make them readable during debugging, also useful alongside JWT decoder when inspecting auth tokens
Minifying JSON before including it in source code or config files
Validating JSON structure before sending to an API or database, convert spreadsheet data first with CSV to JSON

Technical specification

Algorithm or formula: JSON.parse to verify and structure, then JSON.stringify with a numeric indent argument (2 or 4) for pretty mode. Sort-keys mode recursively sorts object keys alphabetically before stringifying. Minify mode stringifies with no indent.
Browser API or library: Native JSON.parse and JSON.stringify. No external library.
Input limits: Bounded by browser memory. Multi-megabyte JSON formats quickly on modern devices.
Output: Formatted, minified, or sorted JSON text. Parse errors include the character offset reported by the engine.
Known limitations: Strict JSON only; comments, trailing commas, and other JSON5/JSONC extensions are flagged as invalid. Order of original object keys is not preserved when sorting.

Frequently asked questions

Does my JSON get sent to a server?: No. All formatting and validation happens in your browser using JavaScript.
What happens if my JSON is invalid?: The tool highlights the error and shows the line and character position of the problem so you can fix it quickly.
Can I format JSON with comments?: Standard JSON does not allow comments. If your input contains them (JSONC format), the tool will flag them as invalid. Remove comments before formatting.
Is there a size limit?: There is no hard limit. The tool processes JSON entirely in browser memory. Very large files (over 10 MB) may be slow.

Reviewed and tested May 26, 2026.