Question 1

Why does it say my JSON is invalid when it looks fine?

Accepted Answer

The usual causes are a trailing comma after the last item, single quotes instead of double quotes around keys or strings, or an unescaped newline inside a string. Validate reports the character position of the first thing it could not parse, so start there.

Question 2

Is my JSON sent to a server?

Accepted Answer

No. The parsing and formatting are done by your browser’s own JSON engine, in the page. That matters here more than on most tools, because config files and API responses routinely carry passwords, keys and personal data.

Question 3

Can formatting change my JSON?

Accepted Answer

Only in one way, and it will tell you. Integers with more digits than a JavaScript number can hold — 64-bit database keys, Discord and Twitter ids — come back rounded, so 12345678901234567890 becomes 12345678901234567000. Formatting names any value that happened to, and quoting it in the source keeps it exact. Nothing else about the document changes but its whitespace and, if you ask, its key order.

Question 4

What does sorting keys do to arrays?

Accepted Answer

Nothing. Array order is meaningful in JSON, so it is left exactly as it was. Only the keys inside objects are reordered, at every level of nesting.

Question 5

Is there a size limit?

Accepted Answer

None imposed by the tool. It is working in your browser’s memory, so the practical ceiling is your own machine - a few megabytes of JSON is unremarkable, a few hundred will be slow.

Free JSON formatter and validator