JSON Formatter and Validator
Paste JSON from an API response, config file or log and make it readable with proper indentation, shrink it to a single line, or check that it is valid. Errors show the line and column where parsing failed.
Paste JSON into the input editor. Choose an indentation, then click Format, Minify or Validate. Copy the result from the output panel.
What is the JSON Formatter and Validator?
The JSON Formatter and Validator is a workbench for JSON (JavaScript Object Notation), the text format most web APIs and many configuration files use. It turns hard-to-read JSON into neatly indented text, compresses it when size matters, and tells you whether it is valid.
What does this tool do?
When you click Format, the tool parses your JSON and prints it again with the indentation you chose (2 spaces, 4 spaces or tabs). Minify removes all unnecessary whitespace to produce the smallest valid version. Validate checks the syntax without changing anything. If the JSON is invalid, you get a plain-language message with the line and column where the problem was found.
How to use the JSON Formatter and Validator
- Paste your JSON into the input editor on the left (or top on mobile).
- Pick an indentation style from the menu if you plan to format.
- Click Format to beautify, Minify to compress, or Validate to check syntax only.
- If there is an error, read the message and go to the line and column shown to fix it.
- Click Copy to copy the output, or Clear to start over.
Key features
Format with your indentation
Choose 2 spaces, 4 spaces or tabs to match your project's code style.
One-click minify
Strip whitespace to reduce payload size before embedding JSON in code or sending it over the network.
Precise error locations
Invalid JSON reports the line and column of the problem, plus a short explanation.
Size and structure summary
See the output size in bytes and the type of the top-level value at a glance.
Local processing
JSON is parsed by your browser's built-in engine. API keys or customer data in your JSON are never uploaded.
Benefits
- Read API responses and logs quickly while debugging.
- Catch syntax errors such as trailing commas and missing quotes before they break a deployment.
- Produce compact JSON for configuration values and network requests.
- Inspect sensitive data safely because nothing leaves your device.
Practical examples
Debugging an API
Paste a one-line API response such as {"user":{"id":42,"roles":["admin"]}} and Format it to see the nested structure clearly.
Finding a trailing comma
A config file fails to load. Validate shows 'Unexpected token } at line 6, column 3' — the line above has a trailing comma that JSON does not allow.
Shrinking a payload
A 4 KB formatted settings object minifies to around 2.5 KB, ready to paste into an environment variable.
Who should use this tool?
- Web and mobile developers
- QA testers inspecting API responses
- Data analysts working with exported JSON
- DevOps engineers editing configuration files
- Students learning how JSON is structured
Common use cases
- Pretty-printing API responses
- Validating configuration files before deploying
- Minifying JSON for embedding or transport
- Locating syntax errors in hand-edited JSON
- Teaching or learning JSON structure
Important limitations
- Only strict JSON is accepted. Comments, single quotes and trailing commas (allowed in JSON5 or JavaScript) are reported as errors.
- Very large files (tens of megabytes) may be slow because they are processed in your browser's memory.
- Formatting does not keep the exact original number formatting — for example, 1.0 is printed as 1.
- Duplicate keys are allowed by the parser, but only the last value for each key is kept in the output.
Frequently asked questions
What does 'Unexpected token' mean?
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The parser found a character it did not expect at that position — often a missing comma, an extra comma before a closing bracket, or a value without double quotes.
Can I paste JSON that contains comments?
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No. Standard JSON does not support comments, so they are reported as errors. Remove them first or use a JSON5-aware tool.
What is the difference between Format and Validate?
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Validate only checks whether the JSON is correct. Format checks it and then rewrites it with clean indentation.
Is it safe to paste API keys or customer data?
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The tool runs entirely in your browser and does not send data anywhere. As a general habit, still avoid sharing secrets where you do not need to.
Which indentation should I choose?
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Two spaces is common in web projects, four spaces in many backend projects. Use whatever your team's code style requires.
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