Good Video Downloader is used to save videos from social networks like Facebook, Twitter, and many others. It's an all-in-one video downloader. You can download audio and video files with flash downloading maintained.

If you want to save a video from a website, you just need to click the icon in the top right of the browser, then you will see a green square plane over the icon. You can choose the video format according to your needs.

And, the best thing is, that you don't need to install anything else. All you need is this extension and your local web browser, then you're good to go.