JSON formatter / validator
Paste raw JSON, pretty-print it with syntax highlighting, and get a clear error if it's invalid. Runs entirely in your browser - nothing is sent anywhere.
Result appears here
This tool checks that your JSON is syntactically valid and pretty-prints it with two-space indentation and colour-coded keys, strings, numbers, booleans, and null values, making nested objects and arrays much easier to read. Use Minify to strip whitespace back out for a compact single-line version.
Everything happens locally in your browser. Nothing you paste here is sent to a server, logged, or stored.
Frequently asked questions
Why does it say my JSON is invalid?
Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or a missing closing brace/bracket. The error message shown comes directly from the browser's JSON parser and usually points at the position of the problem.
Does this support JSON5 or JSONC (comments)?
No, this validates strict JSON only. Comments and trailing commas will be reported as errors.
Is there a size limit?
No hard limit is enforced, but very large payloads (multiple megabytes) may be slow to format since everything runs in your browser tab.