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PROTEGO

JSON Formatter & Validator

Format, validate, and minify JSON instantly in your browser. Syntax error detection with descriptive messages. No data sent to servers.

✓ Free✓ Client-Side✓ No Registration✓ Instant Results
Input JSON
0 chars
Output

JSON Syntax Quick Reference

Valid JSON Data Types

string: "hello world"

number: 42 or 3.14

boolean: true or false

null: null

array: [1, 2, 3]

object: {"key": "value"}

Common JSON Errors

  • ✗ Trailing comma after last item
  • ✗ Single quotes instead of double quotes
  • ✗ Unquoted property names
  • ✗ Comments (JSON does not support comments)
  • ✗ Missing comma between items
  • ✗ Unescaped special characters in strings
  • ✗ Mismatched brackets or braces

Frequently Asked Questions

Is my JSON data safe when using this tool?
Yes. This JSON formatter runs entirely in your browser using JavaScript. Your JSON data is never sent to any server. All processing happens locally on your device.
What is JSON formatting?
JSON formatting (also called JSON beautifying or pretty-printing) adds indentation and line breaks to make JSON data human-readable. Minified JSON removes whitespace to reduce file size.
What is JSON validation?
JSON validation checks if your JSON follows correct syntax rules (RFC 8259). Common errors include missing quotes, trailing commas, unescaped special characters, and mismatched brackets. Our validator pinpoints the exact error.
Can I format JSON with tabs instead of spaces?
Currently our tool supports 2-space and 4-space indentation, which are the most common standards. Tab indentation can be added by pasting formatted output into your code editor.
Does the JSON formatter accept comments, trailing commas or single quotes?
No. The tool uses the strict JSON standard, so comments, trailing commas, single-quoted strings and unquoted keys are reported as errors. Formats such as JSONC or JSON5 allow these, but they need to be converted to plain JSON before standard parsers will accept them.
Why did a large number change after formatting?
The browser parses JSON numbers as JavaScript numbers, which are exact only up to 9007199254740991. Larger integers, such as some database or social media IDs, are rounded when the JSON is re-serialized. If exact values matter, keep those IDs as strings.
Can this tool validate JSON against a schema?
No. Validate checks that the text is well-formed JSON. It does not check required fields, value types or allowed values. For that you need a JSON Schema validator in your code or CI pipeline.

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What the JSON Formatter does

The Protego JSON Formatter formats (pretty-prints), minifies and validates JSON in your browser using the browser's built-in JSON parser. Paste an API response, a config file or a log entry and get readable output with 2 or 4 space indentation, a compact single-line version, or a clear error message when the syntax is broken.

Nothing you paste is uploaded to a server. That matters when the JSON holds access tokens, customer records or internal configuration, which is common when you are debugging an API or a cloud resource definition.

How to use it

  1. Pick a mode: Format / Beautify, Minify or Validate. In Format mode, choose 2 or 4 spaces of indentation.

  2. Paste your JSON into the Input panel, or click Load Sample to try it with example data.

  3. Click the action button (Format JSON, Minify JSON or Validate JSON).

  4. Check the badge on the Output panel: Valid JSON, or Invalid JSON with the parser error. Use Copy Output to copy the result.

Reading the output and errors

Error messages

Errors come from your browser's own JSON parser, so the wording differs between Chrome, Firefox and Safari. Most point to the position where parsing stopped. The real mistake is often just before it: a missing comma, a trailing comma, or a quote that was never closed.

Valid is not the same as correct

Validate checks syntax only. It does not know which fields your API expects or what type each value should be. Valid JSON can still be rejected by an application that expects a specific schema.

Re-serialization side effects

Formatting parses and rewrites the data. If an object repeats a key, only the last value is kept. Integers larger than 9007199254740991 (2 to the power of 53, minus 1) can lose precision, which matters for large IDs.

Minify for transport, format for people

Minified JSON removes whitespace to save bytes in API payloads and environment variables. Formatted JSON is for reviewing, diffing and code review. The data is identical either way.