BlockChan is a free Chrome extension developed by lugg3. It falls under the category of Browsers, specifically Add-ons & Tools. This extension aims to help users block content on 4chan and 4channel.

With BlockChan, if the first message of a thread contains a word that is on the blocklist, all image thumbnails in that thread will be hidden. However, users can still open the images by clicking on them. The blocklist is customizable and can be edited in the popup menu.

Additionally, BlockChan provides a convenient feature where right-clicking the first thumbnail in a thread gives users the option to hide or show all thumbnails in that specific thread.

Overall, BlockChan is a useful tool for those who want to filter out specific content on 4chan and 4channel, providing a more tailored browsing experience.