Free Online JSON Validator & Syntax Checker

Paste JSON below to check for syntax errors. Runs entirely in your browser.

How to validate JSON online

  1. 1

    Paste your JSON

    Copy in the JSON text you want to check, from an API response, config file, or code snippet.

  2. 2

    Click "Validate"

    The tool runs it through a strict JSON parser right in your browser.

  3. 3

    Read the result

    A green checkmark means the syntax is valid. An error message points to exactly what's wrong, like a trailing comma or unquoted key.

  4. 4

    Fix and re-check

    Correct the flagged issue and validate again until you get a clean pass.

Example use cases

1

Catching a broken API payload

Paste a request or response body before sending it to find a stray comma or mismatched bracket.

2

Checking a hand-edited config

Verify a manually edited .json config file parses correctly before deploying it.

3

Reviewing data before import

Confirm a JSON export from another system is well-formed before loading it into your app or database.

Frequently asked questions

What does a JSON validator check?

It checks that your text follows valid JSON syntax — matching brackets and braces, correctly quoted keys and strings, no trailing commas, and valid value types — and tells you exactly what's wrong if it doesn't.

Is my JSON data uploaded anywhere?

No. Validation runs entirely in your browser using JavaScript's built-in JSON parser — nothing is sent to a server.

What's the difference between this and the JSON Formatter?

This tool focuses purely on catching syntax errors. The JSON Formatter also validates, plus pretty-prints and minifies valid JSON.

Why do I get an error even though the JSON looks fine?

Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or a stray comment — none of which are valid in standard JSON even though some JavaScript parsers tolerate them.