Online JSON Validator & Syntax Checker

Validate JSON structure and syntax with precise error messages and line/column pointers.

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How to use

Paste or type your input in the left editor
Adjust options in the toolbar if available
Copy or download the output from the right pane

This free online tool runs entirely in your browser. No sign‑up, no server uploads.

About JSON Validator

Validate JSON structure and syntax with precise error messages and line/column pointers.

The JSON validator runs a full parse of your input according to RFC 8259, the official JSON standard. It tokenizes the raw text into structural elements (braces, brackets, colons, commas, strings, numbers, literals) and builds a parse tree. If any token violates the grammar rules, the parser halts and reports the exact character offset, which is then mapped to a line and column number in the editor for instant visual feedback.

Use the left editor to enter your data. The output updates in real time. You can copy, clear, download, or expand either pane.

Tip: Use the search bar to quickly switch between tools.

Sample JSON

{
  "name": "Jane",
  "age": 29,
  "skills": ["js","html","css"]
}

Example input shown above. Output appears in the right pane instantly.

Why this tool?

Feature	JSON Validator	Typical alternatives
Free online tool	Yes	Often yes
Client‑side only (privacy)	Yes	Varies
No sign‑up required	Yes	Varies

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FAQs

What JSON syntax errors does the validator detect?

The validator catches all common JSON syntax errors including trailing commas, single-quoted strings, unquoted property keys, missing colons or commas, mismatched brackets and braces, and invalid escape sequences. Each error is reported with its exact position in the input.

Does the validator check against JSON Schema?

The primary validation is syntactic — it verifies that your input conforms to the JSON specification (RFC 8259). For structural validation against a JSON Schema, you would paste both your data and schema to check compliance with defined types and constraints.

Can I validate JSON with comments or trailing commas?

Standard JSON does not allow comments or trailing commas, so the validator will correctly flag these as errors. This helps you catch issues before sending data to APIs or parsers that strictly follow the JSON specification.

How is this different from just using JSON.parse() in the console?

While JSON.parse() only throws a generic SyntaxError, this online JSON validator pinpoints the exact line number, column, and type of error. It also highlights the problematic section in the editor so you can fix the issue immediately.

Can I validate JSON from an API response URL?

You can paste any JSON text directly into the validator, including responses copied from browser DevTools, curl output, or Postman. The validation runs entirely in your browser, so your data never leaves your machine.

Does the validator support JSON5 or JSONC formats?

The validator strictly validates against the official JSON specification. Inputs using JSON5 or JSONC extensions — such as comments, unquoted keys, or trailing commas — will be flagged as invalid, helping you ensure compatibility with standard JSON parsers.