Format and beautify
Turn compact JSON into readable, consistently indented text using two spaces, four spaces, or tabs.
FORMAT · BEAUTIFY · VALIDATE
JSON Formatter
Paste JSON. Get a clean result instantly.
Ready — paste JSON to begin.
Invalid JSON
Input
Output
WHAT IT SUPPORTS
The useful parts, without the clutter.
Validate precisely
Find invalid JSON with the exact line and column, plus a focused excerpt that shows where parsing stopped.
Inspect large structures
Switch from formatted text to a collapsible tree and scan objects, arrays, values, and nested keys.
Stay private
Your JSON is processed locally. Nothing is uploaded, stored, or sent to a server.
BEFORE YOU TRUST THE OUTPUT
A formatter can change valid JSON.
This page parses with the browser's JSON.parse() and writes with JSON.stringify(). That is fast and private, but it is a parse-and-serialize round trip—not a whitespace-only text edit. The cases below were reproduced in this tool and checked against the JSON and ECMAScript standards.
LARGE INTEGERS
An ID can lose a digit
Measured here: {"id":9007199254740993} formats as {"id":9007199254740992}. RFC 8259 identifies integers from -(2**53)+1 through (2**53)-1 as the range where common implementations agree exactly. If a long integer is an identifier rather than a quantity, send it as a quoted string before formatting.
EXTREME NUMBERS
A huge exponent can become null
Measured here: {"n":1e400} formats as {"n":null}. The parser produces a non-finite JavaScript number; the ECMAScript serialization algorithm writes non-finite numbers as null. A successful parse therefore does not guarantee a value-preserving round trip. Compare critical numeric fields before copying the result.
OBJECT KEY ORDER
Integer-like keys may move
Measured here with “Sort keys” off: {"2":"b","1":"a","x":0} comes back with "1" before "2". ECMAScript lists array-index property keys in ascending numeric order before other string keys. JSON objects are unordered for interchange, but a textual diff, signed payload, or snapshot test may still care about the original byte order.
BYTE ORDER MARK
An invisible first character can fail
Measured here: a leading U+FEFF produces an error at line 1, column 1. RFC 8259 says generators must not add a byte order mark to network-transmitted JSON, while parsers may choose to ignore one. If JSON looks correct but fails at its first character, remove the BOM in the producing system or a text editor, then validate again.
UNICODE EDGE CASE
Valid grammar can still be unsafe to exchange
Measured here: {"s":"\uDEAD"} parses and formats. RFC 8259 warns that a single unpaired UTF-16 surrogate can produce unpredictable behavior across receivers, including different string lengths or runtime failures. A green validation result only confirms that this browser accepted the text; it does not prove every downstream implementation will handle that string consistently.
SAFE HANDOFF
What to check before you paste it back
For logs and ordinary API inspection, format and copy. For IDs, money, signatures, hashes, fixtures, or cross-language payloads, keep the raw input beside the output. Compare long numbers, exponent-form numbers, and key order. Validate the formatted result in the system that will actually consume it. Formatting makes structure readable; it is not a proof that every value survived unchanged.
Evidence note: The five input/output observations above were run in this page in Chrome on October 2, 2026. The linked RFC Editor and TC39 pages are the primary specifications used to explain the results.
HOW TO USE IT
Three steps. No setup.
- Paste JSON into the input panel or open a local JSON file.
- Select an indent style, optionally sort keys, then choose Format, Minify, or Validate.
- Copy the result, download it, or explore it in the tree view.
FAQ
JSON formatter questions
What is a JSON formatter?
A JSON formatter makes JSON easier to read with indentation and line breaks. Most everyday values round-trip unchanged, but browser number limits, integer-like keys, BOMs, and malformed Unicode can produce the edge cases documented above.
Is this JSON formatter online free?
Yes. This free JSON formatter runs entirely in your browser and does not require an account.
Is a JSON beautifier different?
No. JSON formatter, JSON beautifier, JSON pretty printer, and JSON indenter describe the same readability-focused operation.
Does this tool upload my JSON?
No. Formatting, minifying, validating, sorting, and tree rendering all happen locally in your browser.