JSON Formatter & Validator

Everything runs in your browser, so you can safely paste API responses, configuration files and payloads containing real data.

How to use the json formatter & validator

Paste your JSON into the input box.

Click Format, Minify or Validate.

Copy the result or download it as a .json file.

Why use the Convert Now json formatter & validator

Precise errors

Line and column numbers, not just a character offset.

Four output styles

Two spaces, four spaces, tabs or minified.

Size reporting

See how much minifying saves.

Safe for real data

Nothing is uploaded or logged.

Reading JSON error messages

The most common JSON failures are a trailing comma after the last item, single quotes instead of double quotes, unquoted keys, and an unescaped quote or backslash inside a string. JavaScript's parser reports a character position, which is precise but unhelpful in a 5,000-line file – so this tool converts it into a line and column number, which is where you actually need to look.

Formatting versus minifying

Indented JSON is for humans: reviewing an API response, diffing a config change, or explaining a structure to a colleague. Minified JSON strips every unnecessary space and newline and is for machines, typically saving 15–30% of the payload size over the wire. Neither changes the data, so you can move between them freely – and the minify option reports exactly how much smaller the result is.

What JSON does not support

There are no comments in JSON, which surprises people configuring tools that accept JSON files. There are no trailing commas either. Dates have no native type and are conventionally passed as ISO 8601 strings. Very large integers can lose precision because JavaScript numbers are doubles, which is why identifiers beyond 2⁵³ should be sent as strings.

Read the guide: How to Create a Strong Password (That You Can Remember)

Frequently asked questions

How do I format JSON?

Paste it into the box and click Format. Choose two spaces, four spaces or tabs depending on your project's style.

How do I find a JSON syntax error?

Click Validate. The error message includes the line and column where parsing failed, so you can go straight to it.

What is JSON minification?

Removing all optional whitespace to produce the smallest valid representation, typically 15–30% smaller for transmission.

Can JSON have comments?

No, comments are not part of the JSON specification. Formats like JSON5 and JSONC add them, but standard parsers reject them.

Is my JSON sent to a server?

No. Parsing and formatting happen entirely in your browser, so it is safe for production payloads and secrets.

Why does my large ID number change?

JavaScript numbers are 64-bit doubles, so integers above 2⁵³ lose precision. Send large identifiers as strings.