I've been using this add-on for 3 years now and despite some issues, it works for saving images on Instagram.

That said, saving videos is completely broken.

Pressing the button does NOT bring up save dialog, so you end up pressing the button a few times.. nothing.

Then like 2 mins later, suddenly multiple save dialogs open up to save this video. In all this time you can just head to a online Instagram video downloading site and download the video, it's faster to do all that (esp. if you bookmark that site).