What are the most common JSON syntax errors?

The most common are: trailing commas after the last element, single quotes instead of double quotes, unquoted property keys, missing commas between elements, and mismatched or missing brackets.

Can a JSON file be valid but still cause problems in my app?

Yes. Valid JSON syntax means the file can be parsed, but the data may not match what your application expects. For structural validation, use JSON schema validation tools.

Is there a difference between a JSON syntax checker and a JSON linter?

They are essentially the same for basic JSON. A linter may additionally flag style issues (like inconsistent indentation) beyond pure syntax errors.

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JSON Syntax Checker

A JSON syntax checker verifies that your JSON follows the rules of the JSON specification: double-quoted keys, no trailing commas, correct nesting, matched brackets. FixTools checks your JSON syntax in milliseconds and points to the exact character that is causing a problem.

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Finds all syntax errors in one pass

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Shows line and column of each error

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Clear plain-language error descriptions

JSON Tool

JSON Validator

All processing happens in your browser — your files are never uploaded to any server.

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How to use this tool

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Paste your JSON and use the Validate button to run a full syntax check.

How It Works

Step-by-step guide to json syntax checker:

1
Paste your JSON
Copy the JSON string you want to check and paste it into the input area.
2
Run the syntax check
Click Validate. FixTools parses your JSON and reports any syntax violations.
3
Fix and recheck
Address each error at the reported position and click Validate again until the JSON passes all checks.