.crx file install in chrome

Update: appears to have stopped working since Chrome 80

Drag & Drop the ‘.crx‘ file on to the ‘Extensions‘ page

1. Settings – icon > Tools > Extensions
   ( the ‘hamburger’ icon in the top-right corner )

2. Enable Developer Mode
   ( toggle button in top-right corner )

3. Drag and drop the ‘.crx‘ extension file onto the Extensions page from step 1
   ( crx file should likely be in your Downloads directory )

4. Install

Source: Chrome YouTube Downloader – install instructions