I encountered an issue which persists since years, it however only happens on some websites... The Websites where this issue appears are: https://pixiv.net/ (when downloading images which can only be seen when logged in) https://danbooru.donmai.us/ How does the issue works? (Steps to reproduce) 1. Open any image you want to save 2. Drag and drop the image to your computer into a directory 3. The image is "corrupted" when you want to display it. In fact it isn't even an image, its a HTML File, usually containing a message like "403 - forbidden" Why does it happen? It seems Firefox tries to re-download the image from the Server while doing drag and drop and usually it does that in a kind of private window? I mean usually the HTML-Files contain "403 Access forbidden" or other messages like "please enable cookies". I know there are ways to save the images, like with the "Save as..." Dialog. But doing that for a lot of images, which each goes into a different directory the "save as feature is very inconvenient to use. My question is: Can I just "save" the image which is already in the Firefox cache? Its already displayed, so why does it even try to re-download it? Especially on slower sites I noticed an annoying long wait to drag and drop images. Seems like a rather bad idea, also just adds unnecessary traffic to the Servers where you download the images from. Beside on some sites with CDNs it just doesn't work and gives you a HTML-File as "png/jpg" image...