JSON Parser
Paste JSON to parse and validate it. Valid input is pretty-printed; invalid input shows exactly what went wrong.
Example
Input
{"name":"CalcCafe","tools":["json","yaml"]}Output
{
"name": "CalcCafe",
"tools": [
"json",
"yaml"
]
}How it works
The parser runs your text through the browser's native JSON engine. If it parses cleanly, you get a formatted, indented version; if not, you get the parser's error message pointing at the problem position.
Good to know
The JSON Parser takes raw JSON text and runs it through the browser's native parser to confirm it is syntactically valid, then re-prints it with consistent two-space indentation. It is built for developers, API integrators, and anyone copying JSON out of logs, network panels, config files, or webhook payloads who needs to confirm the data is well-formed before using it. Because parsing happens locally, you can safely check tokens, request bodies, and other sensitive payloads without sending them to a server.
Reach for it whenever JSON arrives as a single unreadable line, when an API returns something you can't visually scan, or when a build step rejects a config file and you need to find the exact character that broke it. It is also a quick sanity check before pasting JSON into code: if the parser accepts it, your application's parser almost certainly will too, since both follow the same strict standard.
To read the result, watch for two outcomes. A valid input is reformatted and indented, which is your confirmation that the structure is sound. An invalid input returns the engine's error message with a position hint such as "Unexpected token" or "Expected property name" near a given offset; start your search at that spot and work backward, since the real mistake (a missing comma, an unclosed brace) often sits just before the reported location.
One caveat worth knowing: strict JSON has no tolerance for trailing commas, comments, single-quoted strings, or unquoted keys, so configuration formats like JSON5 or JSONC will be flagged as errors here even though some tools accept them. Also note that JSON object key order is preserved as written but duplicate keys are silently collapsed to the last value, so if pretty-printing seems to drop a field, check whether you had a repeated key.
Frequently asked questions
What does the parser do with invalid JSON?
It shows the exact syntax error (for example a trailing comma or unquoted key) so you can fix it quickly.
Does it change my data?
No — parsing and re-printing preserves your values exactly; only whitespace and formatting change.
Is my JSON uploaded anywhere?
No — everything runs in your browser with JavaScript. Your data never leaves your device, so it's safe for sensitive payloads and works offline once loaded.
Is this tool free?
Yes, completely free with no sign-up and no limits.
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People also ask
What is the difference between parsing and validating JSON?
Validating only confirms whether the text follows JSON syntax rules, while parsing converts that text into a structured value the program can work with. In practice this tool does both at once: a successful parse is itself proof that the JSON is valid.
Why does my JSON fail with a trailing comma?
The JSON standard does not allow a comma after the last item in an object or array, so {"a":1,} is invalid even though many programming languages permit it. Remove the final comma to make the input parse cleanly.
Can a JSON parser handle very large files?
Browser-based parsing loads the entire input into memory at once, so it works well for typical payloads but can slow down or run out of memory on files of many tens of megabytes. For very large datasets, a streaming parser is usually a better fit.
Does pretty-printing change the meaning of my JSON?
No. Indentation and line breaks are whitespace that JSON ignores between tokens, so a formatted version represents exactly the same data as the compact one. Only the visual layout changes, not the values or structure.
Why does the parser reject keys without quotes?
In strict JSON every object key must be a double-quoted string, so {name:"x"} is invalid and must be written as {"name":"x"}. Unquoted keys are an object-literal feature of JavaScript, not part of the JSON format.
How do I read a JSON syntax error message?
Error messages typically name what the parser expected versus what it found, often with a line, column, or character position. Look at that location and the text immediately before it, since a single missing bracket or comma there can cause the error to surface a little further along.
Is JSON case-sensitive?
Yes. Object keys are case-sensitive, so "name" and "Name" are different keys, and the literals true, false, and null must be lowercase. Writing True or NULL will cause a parse error.