Idmgcext.crx [upd] -

That handy button that appears over YouTube or Vimeo videos.

In these cases, you have to manually use the idmgcext.crx file to restore functionality. idmgcext.crx

Most of the time, IDM installs this extension automatically. However, Google Chrome’s security policies or browser updates often disable or remove it. When this happens, IDM stops catching downloads, and you're left with the browser's slow, basic download manager. That handy button that appears over YouTube or Vimeo videos