JSON Syntax Checker

Check JSON syntax online and see exactly where it breaks. Free, private, no signup.

Quick answer: Validate, beautify and clean JSON, CSV, XML and YAML.

How to use the JSON Syntax Checker

Validate, beautify and clean JSON, CSV, XML and YAML.

The Data Formatter checks and tidies JSON, CSV, XML and YAML. It shows the exact line and column of an error, can fix common JSON mistakes, and cleans CSV by trimming spaces, removing empty rows and columns and dropping duplicates. Developers use it to read API responses, analysts to prepare files before an import. The result can be copied or downloaded, and your text never leaves your device.

Paste or upload your data
Choose the options
Copy or download the result

Tips

After valid JSON, use Edit as a table or Convert to CSV or Excel to carry on in another tool.
Invalid JSON shows the exact line and column. “Auto-fix” repairs comments, trailing commas and single quotes.
Numbers and key order are kept exactly as written – nothing is rounded.
CSV: any delimiter is detected automatically; pick the one you want for the output.
YAML: comments are kept, and you can convert YAML → JSON or paste JSON to get YAML.

Example

Input: {"a" 1}

Output: Error: expected : at line 1

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Who uses Data Utility

Frequently asked questions · Data format benchmark

Frequently asked questions

Why does my JSON say unexpected token?

Usually a missing comma or quote, a trailing comma, or a comment. The checker shows the line and column.

Will large numbers change?

No. Unlike many tools, long numbers like 12345678901234567890 are kept as they are.

What can the Data Formatter do?

Validate, beautify, minify and clean JSON, CSV, XML and YAML. Errors show the exact line and column, and JSON can be auto-fixed for common mistakes such as trailing commas and single quotes.

Data Formatter: JSON, CSV, XML and YAML: Validate, beautify and clean JSON, CSV, XML and YAML for free. Highlight columns, rows and words and download as Excel. Runs in your browser.
JSON Formatter and Validator: Beautify, minify and validate JSON online for free. It shows the exact line of an error and can auto-fix common mistakes. Runs in your browser.
CSV Formatter and Cleaner: Clean a CSV online for free: trim spaces, drop empty or duplicate rows, change the delimiter and tidy headers. Runs in your browser.
XML Formatter and Validator: Beautify, minify and validate XML online for free. It shows the line and column of any error so you can fix it fast. Runs in your browser.
YAML Formatter and Validator: Format and validate YAML online for free, or convert YAML to JSON in one click. Errors show the exact line. Runs in your browser, no upload.
JSON Validator Online: Validate JSON online and see the exact line and column of any error. Auto-fix comments, trailing commas and single quotes. Free, in your browser.
JSON Minifier: Minify JSON online to remove spaces and line breaks and make the file smaller. Free, runs in your browser, nothing is uploaded.
XML Validator Online: Check if your XML is well-formed and find the exact line and column of the first error. Free, in your browser, nothing is uploaded.

Topic guides

JSON Guides and Free JSON Tools