JSON Formatter and Validator Online
Paste JSON and get it pretty-printed with consistent two-space indentation. Invalid input reports the underlying parse error rather than silently failing.
How it works
JSON has no comments, no trailing commas, and no unquoted keys. Those three rules account for most of the syntax errors people hit, and they are worth checking first when the validator complains.
The error this tool shows is the one from the browser's own JSON parser, which includes the character offset where parsing failed. That is usually enough to find the problem by eye; in most cases it is the line immediately before the reported position.
A trailing comma is the most common cause. `{"a": 1,}` is invalid JSON even though it is valid JavaScript, and it is the single most frequent reason a config file will not parse.
Formatting here uses two-space indentation, which is what most linters and formatters expect. Prettier and many editor integrations default to two spaces as well, so formatted output from here will usually be stable when you run it through the formatter again.
This is a formatter and a validator, not an editor. It does not reorder keys, normalise numbers, or apply any schema. It tells you whether the input parses and lays it out consistently.
Use the JSON Formatter and Validator
Paste json on the left to see the result.Runs entirely in your browser — nothing you paste is uploaded or logged.
Worked examples
Real input and the exact output this page produces.
Example 1
JSON
{"name":"Ada","langs":["en","fr"]}
Formatted JSON
{
"name": "Ada",
"langs": [
"en",
"fr"
]
}
Frequently asked questions
Why does my JSON fail to parse?
Most often a trailing comma, a single-quoted string, or an unquoted key. JSON requires double quotes around all strings and property names, and no trailing commas anywhere.
Can it handle very large files?
Yes. Parsing happens in your browser with no upload, so the only limit is the memory available in the tab.
Does it validate against a schema?
No. It checks that the input is well-formed JSON and then formats it. Schema validation is a separate concern.
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