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Free Online JSON Validator

Validate, format, and minify JSON instantly, and auto-fix broken JSON with AI.

Want to master JavaScript data handling?

Our JavaScript Core course covers objects, arrays, JSON.parse(), async data fetching, and more.

load example:
Invalid JSON
1
2
3
4
5
6
7
8
9
10
Syntax Error
Line 8Col 3

Unexpected token ']', ..."aming", ], "acti"... is not valid JSON

Line 8
],

to unlock AI auto-fix. Included in the Free plan.

Common JSON mistakes
Trailing comma
{ "a": 1, }
→ Remove last comma
Single quotes
{ 'key': 'val' }
→ Use double quotes
Unquoted keys
{ key: "val" }
→ Quote all keys
Comments
{ // comment "a": 1 }
→ Remove comments
undefined / NaN
{ "a": undefined }
→ Use null instead

About this tool

JSON Validator

A JSON validator checks whether your JSON is syntactically correct and pinpoints the exact line and character where it breaks. Paste your data to validate it instantly, then format (beautify) it for readability or minify it to save space.

When JSON is malformed, the built-in AI autofix can repair common mistakes - trailing commas, missing quotes, unbalanced brackets - and explain what went wrong. Everything runs in your browser and is free on the HACKUP Free plan.

Frequently asked questions

JSON Validator FAQ

What is a JSON validator?
A JSON validator parses your JSON and confirms whether it is valid. If it is not, it shows the exact location and reason for the error so you can fix it quickly.
What is the difference between formatting and minifying JSON?
Formatting (beautifying) adds indentation and line breaks to make JSON human-readable. Minifying removes all unnecessary whitespace to make the payload as small as possible for transmission.
Can it fix invalid JSON automatically?
Yes. The AI autofix repairs common errors such as trailing commas, single quotes, and missing brackets, and explains the correction.
Is the JSON validator free?
Yes. Validating, formatting, minifying, and AI autofix are all included in the HACKUP Free plan.