Is my JSON uploaded anywhere?

No. The document is parsed in your browser tab with JSON.parse. It is not uploaded, stored on a server, saved to an account or shared by this tool. Even so, never paste passwords, API keys or access tokens into any website tool.

Does formatting change my data?

No. Beautifying and minifying change whitespace only. The tool does not sort keys, repair invalid JSON or change values.

Why does the validator reject comments and trailing commas?

Comments, trailing commas, single quotes and unquoted keys are JavaScript or JSON5 habits, not standard JSON. Remove them or convert the document first; this tool reports the parser error instead of guessing a repair.

Why is there no exact error position for some mistakes?

Browsers report positions differently. When the parser error includes a position, this tool converts it to line and column. When it does not, the tool shows the parser's own message and says the exact position is unavailable rather than inventing one.

Can this tool check whether my API will accept the JSON?

No. It validates syntax only. It does not check a JSON Schema, required fields, field types or business rules, so a syntactically valid document can still be rejected by an API.

What happens with repeated keys and very large numbers?

Standard JSON.parse keeps only the last value when a key repeats, and whole numbers beyond 2^53−1 can lose precision. Keep identifiers and large counters as strings when exact digits matter.

JSON онлайн — форматирование и проверка