Is my JSON uploaded to a server?

No. Formatting and minifying both run in your browser using the built-in JSON parser. tool4.dev never receives the document you paste.

Does it validate JSON as well as format it?

Formatting is validation. The document has to parse before it can be rewritten, so invalid JSON produces the error instead of the output, naming the line and column of the first problem. There is no separate check to press.

Can it format very large JSON files?

Local files up to 10 MiB are accepted. Larger files are rejected before they are read, because parsing them in a browser tab would block the page.

Formatters / LOCAL TOOL

JSON Formatter & Validator

Format, minify, and validate JSON directly in your browser.

Runs locally — input is never uploaded

JSONPaste, type, or drop JSON

Sort

Indent

WHAT IT DOES

A JSON formatter that does not need your JSON.

Enter a JSON object, array, string, number, boolean, or null. Format rewrites it with the indentation you choose, and Minify strips every byte of insignificant whitespace. Both parse first, so a syntax error is reported with its line, its column, and the text around it rather than as a bare verdict. Parsing uses the browser's own JSON engine, so the result matches exactly what your application will see.

Why use it?

Use it when compact or inconsistently indented JSON makes a payload difficult to read. Formatting exposes structure; it does not verify your application's data rules.

How to use this tool

Paste JSON, drop a local file, or load the worked example below.
Choose indentation and format the document. Use the reported position to correct syntax errors.
Review the result and copy it. If field types or required values matter, check them against a schema as a separate step.

Details and limitations

Indentation is configurable between 1 space, 2 spaces, 4 spaces, and tabs.
Syntax errors report the line and column whenever the browser exposes a position.
Line numbers count real newline-delimited lines; long lines scroll rather than soft-wrap.
Local .json files up to 10 MiB can be dropped onto the page or pasted from the clipboard.

WORKED EXAMPLES

Readable structure without changing a number into text

Format this compact document. Then try changing count to the quoted string "2": it still parses, but its meaning and type change. Use schema validation when a number is required.

JSON

{"count":2,"items":[{"id":"a","active":true},{"id":"b","active":false}]}

Expected result

Indented JSON with count still a number, two items in the same order, and boolean active values. Formatting checks syntax, not whether the inventory is correct.

COMMON QUESTIONS

JSON Formatter questions

Is my JSON uploaded to a server?: No. Formatting and minifying both run in your browser using the built-in JSON parser. tool4.dev never receives the document you paste.
Does it validate JSON as well as format it?: Formatting is validation. The document has to parse before it can be rewritten, so invalid JSON produces the error instead of the output, naming the line and column of the first problem. There is no separate check to press.
Can it format very large JSON files?: Local files up to 10 MiB are accepted. Larger files are rejected before they are read, because parsing them in a browser tab would block the page.