How It Works
- Paste or type your raw JSON string, object, or API payload into the editor.
- Pick an indentation style («2 spaces», «4 spaces», or «Tab») and optionally check «Sort keys», then click «Format» (or press Ctrl+Enter) — or click «Minify» for a compact single-line string.
- If validation fails, check the «Line X, column Y» error banner; the editor automatically moves your cursor to the invalid token.
- Check the status badge (e.g., «✓ Valid JSON · 3 keys · 68 B»), then click «Copy» or «.json» to download as data.json.
About JSON Formatter & Validator
Strict RFC 8259 / ECMA-404 validation: verifies that all property names and strings use double quotes, flags trailing commas after the last element, and checks matching braces and brackets.
Tested example: pasting a 59-byte object with a trailing comma triggers «Line 5, column 1» and selects the closing brace; removing the comma and clicking «Format» with 2 spaces outputs «✓ Valid JSON · 3 keys · 68 B» (or «55 B» when minified).
«Sort keys» recursively sorts object keys alphabetically at every nesting level while preserving array item order — ideal for comparing two JSON configuration files or API responses.
100% client-side privacy: unlike server-side validators, JSON.parse and JSON.stringify run entirely inside your browser tab so JWT tokens, API keys, and payloads never leave your device. Note that unquoted 64-bit integers above 9,007,199,254,740,991 should be stored as strings to avoid IEEE-754 rounding, and duplicate keys in the same object keep only the last value.
Frequently Asked Questions
How do I validate and verify if a JSON string or file is valid?
Paste your JSON string or file contents into the editor and click «Format» (or «Minify»). If the structure conforms to RFC 8259, a green «✓ Valid JSON» badge appears with the top-level key/item count and byte size. If invalid, a red banner displays the exact «Line X, column Y» syntax error and highlights the offending character.
Why does valid JavaScript object syntax fail JSON validation?
Standard JSON (RFC 8259) is stricter than JavaScript object literals. It requires double quotes ("") around all keys and strings, forbids trailing commas after the last item in an object or array, and rejects single quotes (''), comments (// or /* */), undefined, NaN, and Infinity.
Does «Sort keys» change the order of items inside JSON arrays?
No. Checking «Sort keys» only sorts object property names alphabetically (recursively across nested objects). Array elements keep their exact original sequence.
How does this compare to server-based validators like CuriousConcept?
Both validate strict RFC 8259 JSON syntax, but this tool executes 100% locally in your browser via native V8/JavaScript parsing with zero network requests, instant cursor jump to «Line X, column Y», recursive key sorting, and one-click minification.
Are large 64-bit integer IDs altered when formatting JSON?
Because browser JSON parsing uses IEEE-754 double-precision numbers, unquoted integers larger than 9,007,199,254,740,991 (Number.MAX_SAFE_INTEGER) can lose precision. Keep 64-bit Snowflake or database IDs wrapped in double quotes as strings.