Free Online JSON Formatter & Validator

JSON Formatter

A JSON formatter adds indentation and line breaks without changing the parsed structure. “Beautify,” “prettify,” and “pretty print” describe the same operation. Choose 2 spaces, 4 spaces, or tabs, then use Format & Validate JSON to check the syntax and create readable output.

This is valid JSON that the formatter can indent:

{
  "name": "4all.tools",
  "active": true,
  "score": 42,
  "notes": null,
  "archived": false
}

JSON Validator

The validator checks standard JSON syntax. It catches errors such as missing or trailing commas, single-quoted strings, comments, unquoted property names, and unclosed braces or brackets. When the browser exposes a useful position, the diagnostic includes the line, column, and nearby context.

This invalid example is missing a comma after the first property:

{
  "name": "4all.tools"
  "active": true
}

Syntax validation is not JSON Schema validation. Validate JSON checks whether the text can be parsed as standard JSON; it does not enforce required properties, data types, or other rules from a schema, and it does not repair the input automatically.

How to Format JSON Online

1. Paste JSON into Input or load one permitted .json file.
2. Choose 2 spaces, 4 spaces, or tabs for indentation.
3. Select Format & Validate JSON.
4. Review Result. Valid input produces formatted JSON; invalid input stays in Input and shows a diagnostic when a location is available.
5. Copy Result or download the current formatted JSON file.

How to Validate JSON Online

1. Paste or load the JSON you want to check.
2. Select Validate JSON without needing to format the text.
3. Look for the Valid JSON status or review the syntax diagnostic.
4. If a line, column, and context are available, use them to correct Input and validate again.

JSON Minifier

Minify JSON parses valid input and serializes it as compact JSON on one line. Minification removes formatting whitespace; it is not file compression and does not create a ZIP or another archive format. The current result can be copied or downloaded.

Local, Client-Side JSON Processing

Formatting, validation, minification, file reading, copying, and download preparation happen locally in your browser. During these operations, the JSON is not sent to an application server and is not stored remotely by this tool.

Frequently Asked Questions

What does a JSON formatter do?

It parses JSON and serializes it with consistent indentation and line breaks so the structure is easier to scan.

How do I format JSON online?

Paste or load JSON, choose an indentation style, and select Format & Validate JSON. Readable JSON appears in Result when the syntax is valid.

How do I validate JSON and locate syntax errors?

Select Validate JSON. Invalid input produces a localized diagnostic and, when the browser provides a recoverable position, its line, column, and context.

What is the difference between formatting and validating JSON?

Validation only checks syntax. Formatting also validates, then creates a pretty-printed result with the selected indentation.

Can I upload a .json file?

Yes. Select or drag one permitted .json file to place its text in Input, then format, validate, or minify it locally.

How do I minify JSON into one line?

Enter valid JSON and select Minify JSON. Result contains compact serialized JSON on one line.

Is my JSON sent to a server?

No. The tool performs its JSON operations locally in the browser and does not send the content to an application server during use.

Does this tool validate against JSON Schema?

No. It validates standard JSON syntax only and does not apply a JSON Schema.

JSON Parsing Limitations

The tool relies on the browser’s JSON.parse and JSON.stringify. Very large integers can lose precision when represented as JavaScript numbers. Duplicate object keys are not reported separately; parsing keeps the last value. Reserializing can therefore change the exact text and cannot guarantee exact preservation of every original value.

JSON5 features, comments, trailing commas, single-quoted strings, NaN, Infinity, and undefined are not standard JSON and are rejected as input. Minifying or formatting changes whitespace and cannot preserve the original lexical representation.