JSON Validator
Developer Tools
Paste any JSON and check whether it conforms to the strict JSON spec. Get an instant pass or a precise error pointing at the first problem.
Runs entirely in your browserAbout JSON Validator
The JSON Validator answers the most common question developers have when an API or config file is misbehaving: is the JSON itself well-formed? It runs the input through the browser's native parser, which is the same code path your application uses, so a pass here is a reliable signal that downstream consumers won't reject the payload for syntax reasons.
On failure, the validator shows the parser's exact error message plus a line and column approximation so you can fix the input in place. It catches trailing commas, unquoted keys, missing brackets, single-quoted strings, and unescaped control characters — the same things a stricter linter would flag. For schema validation (required fields, value types), use a dedicated JSON Schema tool; this validator focuses purely on syntax.
How to use
- 1
Paste JSON into the editor
Drop your JSON into the input. Validation runs as you type — no submit button needed.
- 2
Read the verdict
A green banner confirms valid JSON and reports the root type (Object / Array) plus the number of keys or items.
- 3
Fix any reported errors
If invalid, the red banner shows the parser's message and an approximate line + column. Edit the offending location and the verdict updates instantly.
- 4
Clear when done
Use the Clear button to reset the input for the next check.
Examples
Catching a trailing comma
Strict JSON does not allow trailing commas. The validator points at the offending position.
Input
{ "items": [1, 2, 3], "ok": true, }Output
Invalid JSON — Unexpected token } at position 34Validating a deeply nested object
Even with extensive nesting, the parser scales linearly. Multi-megabyte payloads validate in milliseconds.
Input
{ "user": { "id": 1, "address": { "city": "Berlin" } } }Output
Valid JSON — root is Object with 1 keyFrequently asked questions
Does this validate against a schema?+
No, this is a syntactic validator only. For JSON Schema validation (required fields, value types, regex patterns) use a Schema-aware tool such as Ajv or an online JSON Schema validator.
Why does it reject comments?+
Strict JSON does not allow comments. If you need comments, you are working with JSONC or JSON5 — both are different formats with their own parsers.
How big a file can I validate?+
The validator handles tens of megabytes without trouble on a modern laptop. Above that you might notice a brief freeze while the browser parses; consider splitting into smaller chunks.
Are the error line and column always accurate?+
We derive them from the parser's position offset, which is correct for browsers that expose it. Some older browsers report only a position number and we translate it to line/column — usually within one character of the true error.
Is my input uploaded?+
No. All validation happens locally in your browser via the built-in `JSON.parse` function. No network requests are made.
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