Idmgcext is an extension that is used by users to install the idm download bar or button on every downloadable video or file. in fact, this is chrome browser's extension that is grabbed to the chrome browser's extension & drop it there.. In the video, you'll learn how to download idmgcext.crx idm chrome browser extension or integration module for your internet download manager.. How to install idmgcext.crx? download the extension from the link above. extract the zip file using winrar or winzip. go to chrome extension page. make sure to enable the developer mode & then click load unpacked extension. now choose the idmgcext.crx folder & click ok & the idm extension will be installed to your chrome browser..