JSON Formatter & Validator

How it works

Paste valid JSON and choose two spaces, four spaces or a tab. Format JSON adds indentation; Minify JSON removes unnecessary whitespace. Objects, arrays and primitive values are supported. Parsing uses the browser’s JavaScript JSON engine. Error details come from that engine and can differ between browsers. The tool does not repair invalid syntax or silently remove trailing commas.

Limits and behavior

Formatting uses JavaScript number precision. Large integer values outside the safe range and non-finite numeric results are rejected to avoid silently exporting rounded identifiers. Quote large IDs as strings or use a lossless parser. Duplicate object keys retain their last value. Ordinary floating-point decimals can be normalized, and negative zero becomes zero. Comments are not JSON.

Example

Input {"name":"DevKit","active":true} becomes an indented object. The string "9007199254740993" remains exact, but the unquoted number is rejected. Inputs are limited to 200,000 characters.

Assumptions and limitations

Start with Load example to see the expected input shape. Replace the example with your own text and choose the relevant operation. Editing an input invalidates the previous output so an old result cannot be copied as if it were current. Copy and download buttons become available after a successful run. Clear removes the visible inputs and output from the page. Limits keep small development tasks responsive; use a local editor or dedicated command-line utility for very large files. A successful transformation does not validate your application logic or make untrusted data safe to execute.

Sources

MDN Web Docs

Frequently asked questions