Formateur JSON
即时格式化、验证和压缩您的JSON。
Free JSON Formatter and Validator Online — Pretty-Print and Minify JSON
Format, validate and minify JSON data instantly in your browser. Real-time syntax error detection with line numbers. No data leaves your browser. No account required.
Pretty-print vs minify: which to use
Pretty-print (format): adds indentation (2 or 4 spaces), line breaks between properties and consistent spacing. Makes JSON human-readable for debugging, documentation and code review. Minify: removes all unnecessary whitespace and newlines, reducing the JSON to the smallest possible representation. Use minified JSON in production APIs, config files and data transfers to reduce payload size. A typical JSON response can be 20-40% smaller after minification.
Common JSON syntax errors and how to fix them
The validator highlights these frequent mistakes: Trailing comma: JSON does not allow a comma after the last item in an array or object (unlike JavaScript). Single quotes: JSON requires double quotes for all strings and property names — single quotes are a JavaScript habit. Unquoted property names: all keys must be in double quotes. Missing colon: every key-value pair needs a colon separator. Incorrect boolean/null: true, false and null must be lowercase — True or NULL are not valid JSON. Unclosed brackets: every [ must have a matching ] and every { must have a matching }.
FAQ
Does the JSON stay in my browser or get sent to a server?
Formatting and validation run entirely in your browser using JavaScript — no data is sent to any server. Your JSON remains completely private.
What is the maximum JSON size I can format?
Up to 10 MB of JSON can be formatted. Larger files may cause browser performance slowdowns.
Can I validate JSON Schema (not just JSON syntax)?
This tool validates JSON syntax only. For JSON Schema validation (checking that data matches a defined schema structure), you need a dedicated JSON Schema validator.
Why is my JSON valid but my API still rejects it?
The API may require a specific schema (required fields, value types) beyond syntax validity. Use JSON Schema validation to check data structure compliance.
Can I convert JSON to other formats (CSV, XML, YAML)?
Not in this tool. JSON-to-CSV and JSON-to-YAML conversion is planned for a future update.
Does it support JSON with comments (JSONC)?
Standard JSON does not support comments — they are a syntax error. JSONC (JSON with comments) is a non-standard extension used by some tools (VS Code settings files). Use the "ignore comments" option to strip comments before validation.
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