JSON formatter and validator
Paste JSON to pretty-print or minify it; if it is invalid, the tool shows the error, its line and column, and highlights the exact character.
🔒 Runs entirely in your browser. Nothing you paste is uploaded or sent to a server.
What makes JSON invalid
JSON is much stricter than JavaScript object syntax. These are the mistakes behind almost every JSON.parse / json.loads error:
| Mistake | Invalid | Valid |
|---|---|---|
| Trailing comma | {"a": 1,} |
{"a": 1} |
| Single quotes | {'a': 'x'} |
{"a": "x"} |
| Unquoted keys | {a: 1} |
{"a": 1} |
| Comments | {"a": 1 // note} |
not allowed at all |
| Python literals | True, None |
true, null |
undefined, NaN, Infinity |
{"a": NaN} |
{"a": null} |
| Leading zeros / hex | 007, 0x1F |
7, 31 |
| Raw line break in a string | "line1⏎line2" |
"line1\nline2" |
Reading the error position
Parsers report the position of the first character they could not accept, which is often after the real mistake. A missing comma is reported at the start of the next key; an unclosed bracket is reported at the very end of the input. Look at the highlighted character and the line just before it.
If you got an error like Unexpected token < in JSON at position 0, you are not parsing JSON at all: the server returned an HTML page (often a 404 or login page). See Unexpected token in JSON for how to debug that.
Format vs. minify
Format (pretty-print) adds indentation and line breaks so humans can read and diff the data. Minify removes all optional whitespace to make the payload smaller for APIs and config storage. Both produce exactly the same data. Sort keys orders object keys alphabetically, which makes two JSON documents much easier to compare.
Your JSON is parsed by your own browser's JSON.parse. It is never uploaded, so it is safe to paste API responses or config files that contain internal data.
Last updated 2026-11-01.