JSON Formatter & Validator

JSON Input

JSON Output

Compare JSON

JSON Tools

How to use this tool

Enter JSON, then select Validate, Format or Minify. Copy and Download use only the current valid output. Open Compare JSON for a separate structural comparison.

Try it: Format {"answer":42}, then Minify to return to {"answer":42}. Invalid JSON produces a field error and no downloadable output.

Limit: Validation checks JSON syntax, not an application schema. JavaScript number precision applies; keep large identifiers as strings.

What makes JSON valid?

JSON is a subset of JavaScript literals, but it enforces strict quoting and structure. The formatter highlights syntax issues before payloads reach APIs or configuration files.

Well-formed rules

  • Keys and string values must use double quotes, not single quotes.
  • Arrays and objects cannot contain trailing commas.
  • Numbers should be base-10; NaN and Infinity are not allowed.
  • Comments are not part of the JSON specification.

Common pitfalls

  • Accidentally copying trailing commas from code samples.
  • Embedding comments in configuration files meant for JSON.
  • Using tabs instead of spaces in environments that require strict formatting.
  • Combining incompatible types when merging objects.

JSON best practices

Consistent formatting keeps diffs readable and ensures automation tools parse data predictably. Adopt these conventions for cleaner payloads.

Use stable ordering

Sort keys alphabetically when generating JSON for configuration or caching to reduce merge conflicts and simplify diff reviews.

Leverage schemas

Validate structure with JSON Schema to catch missing fields or incorrect types before data reaches production.

Minify for transport

Compact JSON before sending it over the wire to reduce latency, but keep formatted versions in version control for readability.

A small JSON validation exercise

Paste {"enabled":true,"retries":3} and choose Format. The result has one property per line; Minify returns the compact form.

Valid JSON

{"enabled":true,"retries":3}

Try adding a comma after 3: validation must fail. JSON requires double-quoted property names and does not allow comments or trailing commas. Formatting validates syntax, not an API schema. Parsing and reserializing can lose precision for integers larger than JavaScript can represent exactly; keep identifiers as strings.

JSON tool FAQ

What makes JSON well-formed?

Well-formed JSON uses double-quoted keys, comma-separated elements, and forbids trailing commas or comments. The validator pinpoints syntax mistakes instantly.

How can I validate JSON against a schema?

Once your JSON parses without errors, use JSON Schema libraries like ajv (Node.js) or jsonschema (Python) to enforce field requirements and data types.

Does the formatter send my JSON to a server?

No. Formatting, validation, and comparison all happen locally so sensitive payloads remain on your machine.

How should I handle large JSON files?

For multi-megabyte payloads, stream or chunk data and rely on command-line tools like jq to avoid browser slowdowns.

What is the difference between formatting and minifying?

Formatting adds indentation and line breaks for readability. Minifying removes whitespace to create compact payloads suited for network transmission.

Choose a developer tool

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Run the AES interoperability guide or read how these tools are checked.