An HTML Decoder is a tool that converts encoded HTML entities back into their original characters. When content is embedded in web pages, special characters like <, >, and & are used to represent <, >, and & to avoid conflicts with the HTML syntax. The decoder reverses this process, transforming the HTML-safe entities into their readable form. This is useful when handling user-generated content, retrieving stored HTML, or reading encoded data. By using an HTML Decoder, developers can ensure the proper display and formatting of content without losing any functionality. Additionally, it aids in debugging and cleaning up improperly encoded web data.