Check JSON syntax and find errors instantly. JSONKit pinpoints the exact line and column of
every problem, live as you type — and never uploads your data.
Input
Output
Paste or type JSON to get started — everything runs locally in your browser
How to validate JSON online
Paste your JSON into the input pane, open a .json file, or drag and drop one.
JSONKit validates automatically as you type — no button needed.
If there is an error, read the status bar: it shows the line and column, and the offending line is highlighted in red on the left.
Click the highlighted line number to jump straight to it, fix the error, and watch the status turn green.
Common JSON syntax errors
Most invalid JSON comes down to a handful of mistakes: a missing comma between object
members or array items, a trailing comma before a closing brace, single quotes instead of
double quotes, an unquoted key, or an unescaped line break inside a string. The validator
reports the first error it hits with its exact position — fix that one and re-check, since
one mistake often masks others further down.
When your input is valid, you also get a pretty-printed, color-highlighted view of the
parsed document, which makes it easy to review structure and spot logic mistakes that
syntax alone cannot catch.
Frequently asked questions
How does the validator find errors?
Your input is parsed with the same strict JSON rules used by browsers and servers (RFC 8259). When parsing fails, JSONKit pinpoints the exact line and column of the first problem and highlights that line in the gutter, so you can jump straight to it.
What kinds of errors can it catch?
All syntax errors: missing or extra commas and braces, unquoted or single-quoted keys and strings, trailing commas, unescaped newlines inside strings, invalid numbers, literal NaN or Infinity, and text left over after a complete JSON value.
Does it validate against a JSON Schema?
Not yet — the validator checks syntax, not structure. It confirms your input is well-formed JSON that any parser will accept, which is the first step in debugging most API and config errors.
Is my JSON kept private?
Yes. Validation happens entirely in your browser with JavaScript — nothing is uploaded, logged, or stored. There are no cookies and no third-party scripts on this page.
What does a valid result look like?
When your JSON is valid, you get a green confirmation with the size of your input, plus a pretty-printed, syntax-highlighted view of the parsed document so you can review it comfortably.