JSON Validator
Paste a document and find out whether it parses. Failures come with a line, a column and the offending snippet, so you can fix the cause rather than hunt for it.
How to use the JSON Validator
- Paste the JSON you want to check into the box.
- Press Validate. A green result means the document parses cleanly.
- If it fails, read the caret line under the snippet — it marks the exact column where the parser stopped.
What "valid JSON" means
JSON is defined by a short specification (RFC 8259). A valid document is exactly one value: an object, an array, a string, a number, true, false or null. Anything else — two objects side by side, a stray comma, a comment — is invalid, no matter how readable it looks.
Validation here means syntactic validation. This tool answers "will a parser accept this?" It does not answer "does this match my schema?" A document can be perfectly valid JSON and still be missing every field your API requires.
The five rules that catch most people
- Double quotes only. Both keys and string values need them.
{'a': 1}is invalid. - Keys must be quoted.
{a: 1}is a JavaScript object literal, not JSON. - No trailing commas.
[1, 2, 3,]fails. - No comments. Strip
//and/* */before validating. - Numbers are plain. No leading zeros, no
+prefix, noNaN, noInfinity, no hex.
Reading the error position
The reported column is where the parser encountered something it could not use — not necessarily where you made the mistake. A missing comma on line 8 is usually reported at the start of line 9, because the parser only notices when it sees a key where it expected a separator. Always check the line above the one flagged.
Frequently asked questions
Does a valid result mean my API will accept it?
It means the syntax is correct. Whether the fields, types and values match what a particular endpoint expects is schema validation, which is a separate step.
Why is an empty string invalid?
A JSON document must contain exactly one value. Empty input contains none, so parsers reject it. If you mean "no data", use null or {}.
Is JSONL or NDJSON valid here?
No. Newline-delimited JSON is many documents in one file. Each line is valid on its own, but the file as a whole is not a single JSON value. Validate one line at a time.
Can I validate a file instead of pasting?
Open the file in any text editor and paste its contents. Keeping the tool paste-only means nothing ever leaves your machine.
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