JSON Formatter & Validator

PRACTICAL GUIDE · UPDATED OCTOBER 17, 2026

Use this JSON formatter with a checkable sample

Format, minify, or check JSON from pasted text or a local UTF-8 file up to 1 MB. Try a sample, clear the workspace, copy the result, or download it as JSON. Choose two, three, four spaces or tabs; syntax validation does not validate your application's schema. Start with a fictional sample so you can check the result directly before working with a larger document.

Try a complete input and output

{"project":"demo","enabled":true,"items":[1,2]}

Select Format to see the nested structure on separate lines. Select Minify to remove layout whitespace. Select Validate to check whether the input parses. Copy now uses the output field, so produce an output with Format or Minify before copying. Validate reports syntax status and keeps an existing current output. Editing the input clears stale output.

Explore and work faster

Switch Output between Text and a collapsible Tree. Expand or collapse all branches; number tokens and duplicate keys remain visible. Use Find to move through keys or values in input or output. Choose indentation, turn on Auto-format, or expand the workspace; Escape exits the expanded view. Line numbers appear with wrapping off. Ctrl/Cmd + Enter formats the input.

More tools contains recursive Sort keys A–Z, Escape as JSON string and Unescape JSON string. Sorting preserves array order and duplicate-key order. Unescape expects a quoted string whose decoded contents are valid JSON. Use as input copies the current result back into the editor; Copy output and Download output use the current result. Tree view is bounded for large documents; Text remains available. Nothing is automatically saved to browser storage.

Diagnose an invalid document

Try adding a comma just before the final closing brace. Strict JSON rejects that trailing comma. Fix the input and validate again. Single-quoted strings, JavaScript comments, and capitalized True or False values are other common causes of errors. Errors show a line and column; the browser selects the location in your input. Fix that area and run the action again.

What successful validation does not mean

A string such as "true" is different from the boolean true. A missing field is different from a field set to null. Those distinctions belong to your API contract, not merely to JSON syntax. This formatter preserves original numeric tokens, including large IDs, decimal spellings and exponents. Duplicate object keys remain in the output and trigger a warning, because other applications may keep only the last value. Key order and string escapes are retained. Whitespace still changes, so keep an original for signed documents.

Processing and a final check

The normal JavaScript path runs in your browser; a form fallback can send content to the server. Avoid private credentials in examples. After copying, paste into your destination and verify the first and last lines. Formatting is useful for inspection, but is not a promise of byte-for-byte preservation for signed documents.

For a working request/response example, try the PHP/AJAX search demo and its downloadable source.