JSON Validator
Check whether your JSON is syntactically valid, with the exact line and column of any error. No signup, nothing sent to a server.
Precise Errors
Pinpoints the exact line and column of the first syntax error.
Catches Common Mistakes
Trailing commas, unquoted keys, and truncated input are all caught.
Local Processing
Your data never leaves your browser. Privacy first validation.
How to Use the JSON Validator
- Paste the JSON you suspect is broken — a config file that won’t load, a request body an API keeps rejecting.
- Click Validate.
- If it’s invalid, read the error banner: it names the exact line and column of the first syntax problem, and the offending line is highlighted in the input pane.
- Fix that spot, validate again, and repeat until you see the green ✓ VALID pill.
Example: Catching a Trailing Comma
Input — invalid JSON
{
"name": "config",
"retries": 3,
}Result
✕ INVALID Line 4, Column 1: Expected double-quoted property name in JSON at position 38 (line 4 column 1)
The trailing comma after 3 makes the parser expect another property — so it fails at line 4, exactly where the closing brace appears instead. Delete the comma and the document validates.
Reading parser errors like this one
JSON parser messages describe what the parser expected next, not always the literal mistake — a trailing comma reports "expected property name", a missing quote often reports an unexpected token further along. The line/column position points at where parsing stopped, so look at that spot and the character or two just before it.
Strict by design
Validation here is strict RFC 8259 JSON — the same rules JSON.parse applies in every browser and in Node. Comments, single quotes, unquoted keys, and trailing commas all fail, which is exactly what you want when the destination is a real parser in production rather than a lenient editor.
Frequently Asked Questions
This validates against strict JSON (RFC 8259): double-quoted keys and strings only, no trailing commas after the last item in an object or array, no comments, and no unquoted keys. If your input is valid JavaScript but not valid JSON — a common source of confusion — it will fail here.
The most common causes are a trailing comma after the last array or object item, single quotes instead of double quotes, an unescaped quote or backslash inside a string, or a duplicate object key (technically parseable, but a frequent source of silent bugs downstream). The error message points at the exact line and column so you can check that spot first.
No — this checks only that the JSON is well-formed (syntactically valid), not that it matches any particular shape, required fields, or data types. Schema validation is a different, heavier problem; this tool answers "is this parseable at all," which is usually the first thing you need to know when debugging a broken payload.
No. Validation happens entirely in your browser — nothing you paste here is ever transmitted anywhere, so it works the same whether you are online or not.
No — like every tool here, inputs at or above 200KB are validated in a background Web Worker rather than on the main thread, so the tab stays responsive even while checking a multi-megabyte file.
Related Tools
JSON Formatter
Make messy, minified JSON readable with customizable indentation.
JSON Beautifier
Pretty-print JSON with the same fast, local engine.
JSON Viewer
Explore JSON as a collapsible, searchable tree.
JSON Minifier
Strip whitespace to compress JSON for transport.
JSON Compare
Diff two JSON documents and highlight the changes.
JSON to CSV
Flatten nested JSON into a downloadable CSV file.