JSON Validator
Check JSON syntax and pinpoint the first error.
Validates syntax and reports the first error.
About JSON Validator
The JSON Validator checks whether a document is syntactically valid JSON and, when it is not, pinpoints the first error so you can fix it quickly. It is built for the everyday QA moment where an API response, a config file or a hand-edited fixture "should be fine" but some consumer refuses to parse it.
Validation runs locally with a strict parser — the same rules production systems apply. That makes it a reliable arbiter when a developer says the payload is fine and your test says it is not: paste it here and the error (or the green result) settles it.
How to use
- Paste the document into "JSON input".
- Click "Validate" to run the check.
- Read the result: valid JSON gets a confirmation, invalid JSON gets the parser error pointing at the first problem.
- Fix the input and validate again; "Load sample" shows a valid example for comparison.
Frequently asked questions
What are the most common JSON syntax errors?
Trailing commas after the last item, single quotes instead of double quotes, unquoted property names, comments (JSON has none) and control characters inside strings. The validator surfaces the first one it hits.
Does valid JSON mean my API response is correct?
It means the syntax is correct. Whether the fields, types and values match your API contract is a separate check — syntax validation is the first gate, not the whole test.
Is JSON5 or JSONC (comments, trailing commas) accepted?
No — this is strict JSON as defined by RFC 8259, which is what most APIs and parsers enforce in production. If your file is JSONC, expect errors on comments and trailing commas.
Related tools
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Format and indent JSON so it is easy to read.
Multi JSON Formatter
Format many JSON blocks at once — even concatenated with no separator.
JSON Minifier
Collapse JSON into a single compact line.
JSON Cleaner
Fix JSON copied from Slack, Word or email — smart quotes, invisible characters, comments and trailing commas.