MB Viewer is a free, offline-first desktop application for previewing and editing technical files. Preview TSX/JSX React components without setting up a development environment. Work with Markdown, KaTeX mathematical expressions, Mermaid diagrams, and multiple files in split or quad views. Built for developers, technical writers, researchers, and AI-assisted coding workflows. No account. No cloud dependency. Just open your files and work. Available for Windows, macOS, and Linux.