This free JSON validator checks your JSON for syntax errors, formats it into a readable indented structure, and minifies it when you are ready to ship. Paste your code, click Format, and the result appears in your browser with no data sent anywhere.
JSON Formatter & Validator
What the JSON Validator Does
JSON (JavaScript Object Notation) is the standard format for moving data between servers, apps and APIs. A single missing comma or unclosed bracket can break an integration. The JSON validator reads your input, confirms the structure is valid, and tells you exactly why it fails when it is not.
- Format (Prettify): adds indentation and line breaks so the data is readable.
- Compress (Minify): removes spaces and line breaks to cut file size.
- Validate: blocks formatting when the syntax is invalid and shows an error message that points to the problem.
- Copy and Clear: copy the cleaned result or reset the editor.
How to Use the JSON Validator
- Paste your JSON into the editor.
- Click Format (Prettify). If the structure is valid, it is indented and ready to read.
- Read the error message if validation fails. Fix the problem and format again.
- Click Compress (Minify) when you want the smallest version for production.
- Click Copy Code to take the result with you.
Common JSON Errors the Validator Catches
- Trailing commas. A comma after the last item in an object or array is not allowed in JSON.
- Single quotes. JSON requires double quotes around keys and string values.
- Unquoted keys. Every key must be a quoted string.
- Comments. JSON does not support comments, so remove them before validating.
- Mismatched brackets. Every opening brace or bracket needs a matching close.
The format rules are defined in RFC 8259, and json.org has a compact visual reference of the grammar.
When to Use a JSON Validator
- API troubleshooting. Paste a webhook payload to confirm the data is valid before you blame the receiving system.
- Reading minified data. Turn a single unreadable line from a server response into an indented tree.
- Server log analysis. Make JSON-formatted error logs readable so you can find the cause quickly.
- Config file checks. Validate a settings file before you deploy it.
- Preparing production files. Minify verified JSON to cut load times.
Tips for Debugging JSON Faster
- Validate small sections first when a large file fails. Isolate the broken object.
- Look at the line the error points to, then check the line above it. A missing comma often shows up on the next line.
- Keep a formatted copy for humans and a minified copy for production.
- Do not paste secrets such as live API keys or passwords into any online tool, even one that runs locally. Replace them with placeholders first.
JSON vs JavaScript Objects
JSON looks like a JavaScript object, but it is stricter. JavaScript allows single quotes, unquoted keys, comments and trailing commas. JSON allows none of them. Code that works in a browser console can still fail when a server or API reads it as JSON, which is why a quick pass through a validator before you send a payload saves a round of debugging. Re-run the check after every manual edit, since one new comma can break a file that was valid a minute ago.
JSON Validator FAQ
Is my JSON sent to a server?
No. The validator runs in your browser, so your data does not leave your device.
What is the difference between formatting and minifying JSON?
Formatting adds indentation so people can read the data. Minifying removes whitespace so the file is as small as possible.
Why does my JSON fail validation?
The most common causes are trailing commas, single quotes, unquoted keys and missing brackets. The error message shows where the parser stopped.
Can the JSON validator fix errors automatically?
It identifies and locates errors. You correct them, then format again.
Related Free Tools
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- Word Counter & Text Analyzer for character counts.
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