What is explain-plan?

Explain Plan is a free, browser-based tool that helps people understand how databases run their queries. When you write a SQL query, the database creates an internal plan for executing it. This tool lets you paste that plan's output and see it as an interactive graph, diagram, table, and statistics view. It also flags potential performance issues automatically. The tool supports PostgreSQL, MySQL, MariaDB, and SQLite. Everything runs directly in your browser. No query is ever executed, and nothing you paste gets uploaded to a server. This matters because database query plans can contain sensitive information about your schema and data patterns. Running purely on the client side keeps that information private while still giving you the visual analysis you need. The tool accepts several input formats for each database engine. PostgreSQL users can paste JSON-formatted EXPLAIN output or plain text from EXPLAIN and EXPLAIN ANALYZE. MySQL and MariaDB users can provide FORMAT=JSON output or ANALYZE text trees. SQLite supports the shell tree format and raw row output. You can pick the database engine yourself, or the tool can detect it from the text you paste. The project is built with Vite, React 19, and TypeScript. It uses Tailwind CSS for styling with a custom dark theme. The core parsing and analysis engine comes from a separate package called @tabularis/explain, which powers a commercial product called Tabularis. Tests are written with Vitest and Testing Library. Development requires pnpm for installing dependencies and running commands like the local dev server, test suite, and production build. The site is a static single-page application, so deployment to Vercel needs no special configuration. SEO settings live in a JSON file that drives page titles, descriptions, social media cards, and structured data. A build-time plugin injects these tags into the HTML, so adjusting SEO never requires touching the application code itself.