JSON formatter and validator

How to use

1. Paste your JSON into "JSON input".
2. Choose an indent (2 spaces, 4 spaces or tab) and press "Format". Press "Minify" for a single line, or "Validate only" to just check it.
3. Press "Tree view" to browse objects and arrays as a collapsible tree. "Expand all" and "Collapse all" switch every level at once.
4. If there is an error, the line, column and nearby text are shown. Fix it and press the button again.
5. Copy the result or download it as a .json file.

Notes and limits

• Input up to 5 MB. Nesting up to 1,000 levels.
• Standard JSON (RFC 8259) only. Comments, trailing commas, single quotes, NaN and Infinity are reported as errors.
• Duplicate keys are not errors: they are kept as written and reported as a warning.
• The tree view handles JSON with up to 20,000 values. Use Format for larger documents.
• A leading BOM is removed. Output uses LF line endings.
• Nothing you enter is saved. It is gone when you close the page.

How it works

Instead of JSON.parse, a small scanner reads the text character by character. Error messages and positions are therefore the same in every browser.

Strings and numbers are copied exactly as written. Large integers above 2^53 keep every digit, 1.0 stays 1.0, 1e400 is not turned into null, and escapes such as \u0041 are kept. Only whitespace and line breaks change.

When a key appears more than once in the same object, the key name, its location (for example $.items[0]) and the line and column are listed. Most programs keep only the last value.

The tree view is built from the same scan, so values are shown exactly as written (large integers keep every digit). Only key names are shown with their escapes decoded.

After minifying, the size before and after (UTF-8 bytes) is shown.