Vimeo Downloader adds "download" button on video page, video list and embedded video. Just click download button, then choose quality of the video to be downloaded. 
Done.

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How it works:

On vimeo.com main page:
Point cursor to video thumbnail and you will see "download" button in upper left corner (down arrow). After clicking this button choose one of downloading options.

Vimeo video (if its available):
Point cursor to video thumbnail and you will see "download" button in upper right corner (down arrow). After clicking this button chose one of downloading options.

Embedded Vimeo video:
You can download videos directly from embed Vimeo players.
Point cursor to video thumbnail and you will see "download" button in upper right corner (down arrow). After clicking this button chose one of downloading options.
If "download" button didn't appear (the reason could be a website-specific individual method of Vimeo video embedding) -  start playing the video and after that "download" button will appear and downloading will become available.

Download using pop-up icon:
Available for downloading Vimeo video files are shown after clicking pop-up icon of the extension.
Number shown on popup icon of the extension corresponds to number of videos available for downloading on the page.
Please note: we just extend your browser functionality with download buttons and if video is not available in desired quality, it's not our fault.

The video is available in poor quality? Usually low quality occurs when author initially uploads video with low quality.