HTMLエラーチェッカー is a free Chrome extension designed to detect errors in HTML code, such as missing start or end tags. This tool provides a straightforward way to check for common HTML mistakes by displaying the number of errors directly in the extension button. It operates without sending data externally, ensuring user privacy while analyzing the source code using JavaScript. Users are advised to temporarily disable the extension on pages with forms if unexpected behaviors occur.

This extension focuses on identifying basic HTML errors, making it an essential tool for web developers and designers. It has gone through several updates, addressing bugs and improving functionality, including the ability to check local files and enhancing privacy settings. The latest version has implemented support for Manifest V3 and includes features like customizable warnings based on regular expressions, allowing for a tailored error-checking experience.