JSON Toolkit - Free Online JSON Formatter, Validator, Diff, Converter & Query Tool

JSON Toolkit is a free, browser-based suite of developer tools for working with JSON data. Format and prettify messy JSON with configurable indentation, or minify it for production. The built-in validator catches syntax errors instantly with clear error messages and line numbers.

Compare two JSON objects side by side with the diff checker, which highlights additions, deletions, and changes using color-coded markers. Convert JSON to YAML, CSV, XML, or TypeScript interfaces with a single click. Query nested JSON structures using JSONPath expressions and view results in real-time.

The graph visualizer renders JSON as an interactive, collapsible tree with color-coded values for strings, numbers, booleans, and null. All processing happens entirely in your browser — no data is ever sent to a server. Built with Next.js, Monaco Editor, and Tailwind CSS.