JSON Validator

How it actually works

Validation is a real parse with the browser's JSON parser, the same strict grammar every JavaScript runtime enforces. There is no approximate checker and no custom grammar subset, so the verdict is exactly what your application will do with the bytes.

When parsing fails, the tool reads the position the engine reported, converts that character offset into a line and column by walking the source, and shows the message beside the coordinates so you can jump to the offending brace in your editor. A passing document also reports its structural counts, so you know the file is not only valid but non-empty.

What that means for your results

The strictness is the value. Trailing commas, single-quoted keys, comments, unquoted property names and Infinity are all rejected here for the same reason they will be rejected by a server parser, which catches the class of bugs that survive hand-editing a config file.

Because the check is a parse rather than a lint, a document that passes is guaranteed to be loadable; nothing about indentation or style is judged, which is why formatting is left to JSON Formatter.

Where it falls short — honestly

Syntax only. The tool cannot tell you that a required field is missing, that a date is malformed or that an enum value is out of range - that is the job of a JSON Schema validator, and a schema-valid document can still be logically wrong.

Error wording comes from the engine, and engines differ: Chrome and Safari report a character position, while some Firefox builds report line and column in the message itself. Where no position can be extracted, the coordinates fall back to the start of the document and the raw message is what you should read.

Large documents are parsed in full, so a multi-megabyte file will be checked but is better handled in an editor with a real parser.

A real end-to-end workflow

Use it as a gate before anything ships: paste a generated config, a fixture or an API contract, confirm the verdict, then fix at the reported line rather than by eye. When the error is an unexpected token, the two usual causes are a comma at the end of the last member and a number written with a leading zero or a trailing period.

If the payload arrived base64-wrapped, decode it first with Base64 Encoder and validate the result; if it arrived as XML and needs comparing, convert with XML to JSON and validate the conversion.