JSON Formatter & Validator

Paste your JSON into the text box above (or upload a .json file), choose your indentation style, then click Run. The formatted output appears instantly — no account required.

You get a validation issues table, not just a single error message. Every problem found in the document is listed at once — no need to fix one error and re-run to discover the next. Each row shows the exact line and column, a plain-English explanation of the cause, and a suggested fix. Fix all the listed issues, then re-run to get the formatted output.

The validator goes beyond a basic parse error and identifies the root cause for all of these patterns automatically: missing commas between values or key-value pairs; trailing commas before a closing } or ]; Python literals (True, False, None — which must be true, false, null in JSON); JavaScript-only values (undefined, NaN, Infinity — none are valid JSON); single-quoted keys or values (JSON requires double quotes); unquoted or numeric object keys; JS-style line comments (//) and block comments (/* … */); an = sign used instead of : between key and value; unterminated strings (missing closing quote); unclosed or mismatched brackets — the checker is string-aware so characters inside values are not miscounted; and typographic 'curly' quote characters that look like standard quotes but are rejected by JSON parsers. A UTF-8 byte-order mark (BOM), common in Windows-saved files, is silently stripped before parsing so it never causes a spurious error.

Yes. Enable the 'Sort keys alphabetically' option before running the tool. All object keys will be sorted A–Z at every nesting level.

The free tier accepts JSON files up to 5MB. Most JSON files are well under this limit — even large API responses or config files typically stay below 1MB.