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JSON Validator

Check JSON syntax and get the exact line, column and cause of any error.

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Quick Tool Overview

The JSON Validator checks a document for syntax errors and reports the exact line, column and cause of the first failure, with the offending line reprinted and a caret under the character that broke it. Valid documents get their structure measured instead.

What it does
Validates JSON syntax and locates errors precisely
You give it
Any JSON document, valid or broken
You get back
A pass or a line, column and cause for the failure
Best for
Debugging API responses, config files and log payloads
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the JSON Validator

Paste a document and the validator tells you one of two things: that it parses, or exactly where it stops parsing. The error is reported with a line number, a column number and the offending line reprinted with a caret under the character that broke it.

Most invalid JSON fails for one of five reasons, and the validator names which one: a trailing comma after the last item in an object or array, keys or strings wrapped in single quotes, an unquoted key, an unescaped line break inside a string, or a bracket that was never closed. When the document is valid you also get its statistics — key count, nesting depth, node count and a breakdown of how many strings, numbers, booleans and nulls it holds.

Key features of the JSON Validator

Errors with a caret, not just a message

The failing line is reprinted with a marker under the exact character, so you fix the problem instead of hunting for it.

Plain-English causes

Trailing commas, single quotes, unquoted keys and unclosed brackets are named as such rather than reported as a generic parse error.

Structure statistics

A valid document reports its key count, node count, maximum nesting depth and a breakdown of value types.

Live as you type

The verdict updates on every keystroke, so fixing an error and confirming the fix is one continuous action.

Nothing is uploaded

Validation uses the browser's own JSON parser, so tokens and personal data inside a payload never leave your machine.

How to use the JSON Validator

  1. 1

    Paste the JSON

    Drop in an API response, a config file or any string you believe is JSON.

  2. 2

    Read the verdict

    A green note means it parses. A red one names the line, the column and the likely cause.

  3. 3

    Fix and re-check

    Correct the character the caret points at. The verdict updates as you type.

  4. 4

    Review the statistics

    Once valid, check the depth and key count to see whether the structure is what you expected.

Frequently asked questions

A trailing comma. JavaScript object literals allow one after the last item and JSON does not, so anything copied out of a code editor tends to carry one.

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