JSON Validator

Paste your JSON and instantly know if it is valid. Pinpoints errors with line and column numbers, flags duplicate keys and deep nesting, and shows a collapsible tree view of the structure.

Paste your JSON above and click Validate JSON to see the result.

About the JSON Validator

This free online JSON validator checks whether your JSON is syntactically valid according to the RFC 8259 standard. It goes beyond a simple pass/fail — pinpointing exactly where errors occur and flagging structural issues that may cause problems in real applications.

Features

Validates JSON syntax against the RFC 8259 standard
Precise error reporting with line number, column number, and description
Detects duplicate keys — valid in some parsers but unreliable across implementations
Warns about deeply nested structures (depth > 8) and very large payloads
Collapsible tree view — explore the full structure of valid JSON interactively
Expand all / collapse all tree controls
Shows node count, max depth, line count, and file size
100% client-side — your data never leaves your browser

How to use

Paste your JSON into the input box (or click Sample to load an example).
Click Validate JSON.
If invalid, the error banner shows the line, column, and description of the problem.
If valid, a collapsible tree view lets you explore the structure interactively.

Common JSON errors

Trailing commas — [1, 2, 3,] is invalid in JSON (unlike JavaScript).
Single quotes — all strings and keys must use double quotes.
Unquoted keys — {name: "value"} is not valid JSON.
Comments — JSON does not support // comments or /* block comments */.
Undefined / NaN / Infinity — these JavaScript values are not valid JSON.