1. Open Audacity, and in the dropdown menu under "Audio Host," choose "Windows WASAPI."
2. In the recording device drop-down, choose your computer's default speakers or headphones. Depending on your setup, you might also need to pick the option labeled "Loopback." This will differ depending on what sort of sound card your PC has.
這個方法萬能，聽見就能錄下，就是花時間。
或用下載工具：
實用電腦： 這個是開源免費無廣告的youtube下載工具 - 由hot_powerz發表 - 文學城 (wenxuecity.com)
