Why is my JSON invalid when it looks fine?

The three usual causes are a trailing comma, a single-quoted string, and a smart quote pasted in from a word processor. The last is invisible in most editors and produces a parse error at a character that looks identical to a normal quote.

Does it check against a schema?

No. It checks that the document is well-formed JSON. Whether it contains the right fields with the right types is a separate question, and one that needs a schema to answer.

Can it handle very large files?

It parses in your browser, so it is bounded by the memory of the tab. Files of a few megabytes are fine; a very large export may be better checked with a streaming parser.

Is NaN or Infinity valid?

No. JSON has no representation for either, though several languages will happily serialise them. A document containing NaN was produced by a non-conforming encoder and will be rejected by conforming parsers.

JSON Validator

Checks whether a document is valid JSON and, when it is not, says which line and column broke it and what was expected there.

Runs in your browser — nothing is uploaded

Your JSON

0 characters0 words0 lines0 B

Try:

Indentation

Sort keys A–ZUseful for diffing two payloads

Shortcut: Ctrl + Enter to format, Ctrl + Shift + K to clear.

Result

Your formatted JSON appears here

Everything runs in your browser — nothing you paste is uploaded or stored on a server.

Need this as an API?

Why use it

Built to be genuinely useful

Points at the problem

The line, the column, and the surrounding lines — not just the word 'invalid'. Most JSON errors are a missing comma several lines above where you were looking.

Knows the usual culprits

A trailing comma, a single-quoted string, an unquoted key and a stray comment are all invalid JSON and all common. Each is named rather than reported as a generic parse failure.

Nothing is uploaded

It runs in your browser. Tokens, keys and customer data routinely end up in these tools, and none of it should have to cross a network to be decoded.

Free, no sign-up

No account, no daily cap, and no feature held back behind a paywall.

How it works

Three steps

1
Paste the JSON.
2
Read the verdict and, if it failed, where.
3
Fix and re-check.

What JSON does not allow, however reasonable it looks

Trailing commas are the most frequent. JavaScript accepts them, most languages accept them in their own literals, and JSON does not. An array ending in a comma before the bracket is invalid, and it is easy to leave behind after deleting the last element.

Comments are not part of JSON either. There is no // and no /* */, however useful they would be in a configuration file. Formats that do allow them — JSON5, JSONC, YAML — are different formats, and a parser expecting JSON will reject them.

Strings must use double quotes, and keys must be quoted. 'name' and name are both invalid where "name" is required. This trips people up most often when JSON has been hand-written from a JavaScript object literal, where all three forms are legal.

Valid is not the same as correct

This page answers one question: does the document parse. It does not know whether the field names are the ones your API expects, whether a required property is missing, or whether a number should have been a string.

That second question is what JSON Schema is for. If you find yourself checking the same shape repeatedly by eye, writing a schema turns it into something a machine can check on every request rather than something you notice when it breaks.

FAQ

Questions people ask

API access

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