JSON Syntax Validator
Validate JSON syntax with exact line, column and path, catch duplicate keys and format or minify — in your browser. It runs entirely in your browser — no signup, no installation, and nothing you paste or drop leaves your device.
Everything runs in this browser tab — nothing is uploaded. Duplicate keys are legal JSON, but most parsers silently keep the last value, so this tool lists them.
About the JSON Syntax Validator
Paste any JSON document into the box above and this validator tells you immediately whether it is syntactically valid — and if it is not, exactly where it breaks. Instead of a vague parse error it shows the line, the column, the path inside the document (for example $.orders[2].total) and a snippet with a caret under the offending character. It also counts objects, arrays, property names and nesting depth, flags duplicate keys that most parsers silently collapse into one value, and warns when an integer is too large for JavaScript to represent exactly. Everything runs locally in this browser tab, so confidential payloads never leave the page, and a valid document can be formatted with two or four spaces (or tabs), minified, copied and downloaded again as a .json file.
Über den JSON Syntax Validator
More free tools
What is JSON Syntax Validator?
JSON Syntax Validator is a free online developer tool built for developers debugging payloads, configs and code. Validate JSON syntax with exact line, column and path, catch duplicate keys and format or minify — in your browser In practice you paste your JSON, run the check to get the exact line, column and path of any error, and then fix duplicate keys, then format or minify the result.
Your code, tokens and payloads never leave the browser, which matters when you are debugging something under NDA or handling production data.
How to use JSON Syntax Validator
- Paste your JSON.
- Run the check to get the exact line, column and path of any error.
- Fix duplicate keys, then format or minify the result.
JSON Syntax Validator FAQ
Is JSON Syntax Validator free to use?
Yes. JSON Syntax Validator is completely free and needs no account, no trial and no payment details. Every feature on the page is available without limits.
Is my data uploaded anywhere?
No. JSON Syntax Validator runs entirely in your browser, so the text, file or number you enter never leaves your device.
Does JSON Syntax Validator work on a phone or tablet?
Yes. It works in any modern browser on desktop, tablet and phone. There is no app to install and no account to create.
How do I use JSON Syntax Validator?
Paste your JSON. Run the check to get the exact line, column and path of any error. Fix duplicate keys, then format or minify the result.