JSON Validator
Check JSON syntax and inspect document structure.
LocalYour data is processed locally in your browser and is not uploaded to Alphzen.
Paste JSON to check syntax. This does not validate schemas.
How to use
- Paste the JSON you want to check.
- Select Validate, or wait — validation also runs as you type after a short pause.
- If the document is invalid, jump to the reported line and fix the syntax.
- If it is valid, review the detected type, size, depth, and key counts.
Features
- Syntax validation using the browser JSON parser — the same rules APIs use.
- Human-readable errors with line and column, not only a raw engine message.
- Document stats: root type, UTF-8 size, line count, depth, and key count.
- Does not claim JSON Schema or API contract validation.
- Processed locally; the payload never leaves this page.
Examples
{ "ok": true, "count": 3 }Valid JSON. Root type: object.
{
"name": "Ada"
"active": true
}The parser fails at the second property because a comma is missing after the first line.
FAQ
Does this validate against a JSON Schema?
No. This tool checks that the text is well-formed JSON. It does not evaluate schemas, OpenAPI contracts, or required fields. Schema validation is a different problem.
What about duplicate keys?
JSON.parse keeps the last value for a duplicate key and does not throw. That is how JavaScript engines behave. If duplicates matter, inspect the source text separately.
Are trailing commas allowed?
No. Trailing commas are valid in JavaScript objects and in some config formats, but they are invalid in JSON.
Related guides
- How to validate JSON (syntax vs schema)JSON can be well-formed and still wrong for your API. Here is the difference between parse errors and schema checks.
- How to format JSON without losing dataWhat pretty printing actually changes, when minified JSON is better, and how to fix the syntax errors that block formatting.
Related tools
About this tool
A JSON validator answers a narrow question: can this text be parsed as JSON? That is the check you want before sending a payload, committing a config, or pasting a response into another tool.
Alphzen reports the first syntax error with a line and column. Typical causes are missing commas, unquoted keys, single quotes, trailing commas, and unescaped newlines inside strings.
Valid JSON can still be the wrong shape for an API. Use this tool for syntax, then check the contract separately. Related tools: JSON Formatter for readability and JSON to CSV for tabular exports.