These online sites allows you to download, watch and saves videos directly from Instagram to your computer files without any need for your phone.

Steps To download video :
1. Open Instagram and click on the video you want to download.
2.  Copy and paste the Url of the Instagram video to the form field in any of the apps.
3. Video will be open in new url and you will be asked ehether to watch, download or save video. Choose the option you desire. Or Right click on the video, choose save video, save video in a file on your computer. 

via Blogger