The HTML Reader plugin enables Obsidian users to view and interact with `.html` and `.htm` files directly within their vaults. It provides multiple operating modes to balance functionality and security, including restricted modes that sanitize unsafe HTML content and unrestricted modes for advanced use cases. Users can customize background colors, define extra file extensions, and utilize hotkeys or gestures for navigation and zooming. The plugin also supports enhanced menu options, allowing for efficient interaction with HTML documents.