HTML Tag Error Checker is a Chrome extension developed by macha that focuses on identifying issues with HTML start and end tags. The program highlights errors in the HTML code of the current web page, pinpointing mistakes like incorrect opening and closing tags.

This extension offers a user-friendly interface by displaying results in a separate tab and indicating the number of errors directly on its icon. Additionally, it provides automatic checking functionality, along with customizable settings for sites to be automatically checked and options to exclude specific websites. Users can also establish custom warning rules to tailor the error-checking process to their needs.