Free Converter
JSON Formatter & Validator
Format, prettify, and validate JSON instantly in your browser. No upload required — completely private and free.
Drag & Drop a JSON file here
Supports .json files. Or paste your JSON in the area above.
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Format, prettify, and validate JSON instantly in your browser. No upload required — completely private and free.
Supports .json files. Or paste your JSON in the area above.
JSON formatting (often called pretty-printing or beautification) takes compact JSON and adds whitespace — line breaks, indentation, consistent spacing — to make the structure visible to human readers. Compact JSON is the right format for transmission: it minimizes bytes over the wire and storage. Formatted JSON is the right format for inspection: indented hierarchy reveals nested structure at a glance, makes diffs meaningful, and lets developers locate specific fields without parsing the document mentally.
This formatter parses the input as JSON to confirm it is valid, then re-emits it with consistent indentation. Invalid input produces an error pointing to the syntax problem. Valid input is reformatted regardless of how compact or messy the source was. Indentation defaults to two spaces, matching the most common JavaScript convention.
The formatter also offers minification (the inverse operation), which strips all unnecessary whitespace to produce the smallest valid JSON. Minified output is useful for production transmission; formatted output is useful for development and debugging.
Reading deeply nested JSON without indentation is essentially impossible — the structure is technically present but invisible. Even moderately complex JSON benefits enormously from formatting. Code reviewers, API debuggers, and anyone trying to understand a data payload need formatted JSON to see what is actually there.
Formatting also catches errors. If JSON fails to parse during formatting, the error message identifies the exact position of the syntax problem — often a missing comma, an unquoted key, or a stray trailing comma that the producing system did not flag. A formatter is the simplest JSON validator available.
Paste JSON, click format.
The formatter uses JSON.parse and JSON.stringify, the same pair every JavaScript runtime ships. Parsing follows RFC 8259 (the current JSON spec), accepting strict JSON but rejecting JavaScript object literals, comments, trailing commas, and other JSON5 extensions.
JSON.stringify accepts an indent argument: a number (spaces) or string (custom indent character, such as a tab). The formatter exposes both options. Output is sorted in source order for objects (since ES2015 preserved property insertion order across all major engines).
Edge cases: large numbers beyond Number.MAX_SAFE_INTEGER lose precision when parsed (a known JSON limitation; use string values for IDs that exceed 2^53). Unicode escapes in strings are preserved literally. Trailing whitespace is stripped from each line.