JSON Formatter & Validator
Beautify, minify, and validate JSON data with syntax highlighting
Tip: click a node to fold · Alt+click to toggle entire subtree · Copy always copies the full JSON.
Frequently Asked Questions
What is a JSON formatter?
A JSON formatter (also known as a JSON beautifier or pretty-printer) re-indents JSON data with consistent whitespace so that nested objects, arrays, and key/value pairs become easy to read. DevToolkit's JSON Formatter also validates syntax as it formats, pinpointing issues such as trailing commas, unclosed strings, or mismatched brackets.
What can I use this tool for?
Typical use cases include debugging API responses, reading structured log data, preparing examples for API documentation, restoring minified JSON to a readable layout, and checking configuration files (package.json, tsconfig.json, etc.) before committing. Use the "Minify" option for the reverse: collapsing JSON into a single line for embedding in code or URLs.
How large a payload can it handle? Are there input restrictions?
The tool runs entirely in your browser, so the practical limit is your device's available memory — multi-megabyte documents format instantly on modern hardware. Input must be valid JSON: strings and keys use double quotes, no comments, and no trailing commas. If you have a JavaScript object literal, convert single quotes to double quotes first.
Why am I seeing an "Unexpected token" or syntax error?
The most common causes are single quotes on keys, unescaped newlines or quotes inside strings, trailing commas, and unbalanced braces. The error message includes a line/column pointer so you can jump straight to the problem. Files generated by non-strict tools may need small fixes before they validate.
Is my data safe? Does it get uploaded to a server?
No. All formatting, minifying, and validation happens locally in your browser. Your JSON never leaves your device and is never logged or indexed. The tool works offline once the page is loaded.
What is the difference between formatting, minifying, and validating JSON?
Formatting (beautifying) adds indentation and newlines for human reading. Minifying strips all unnecessary whitespace for efficient transfer. Validating only checks that the document conforms to the JSON spec without changing it. DevToolkit bundles all three into a single tool you can switch between with one click.