Been looking for addons like this as quite a few similar "no Save-As window" addons broke with the switch to webextensions. One issue (perhaps due to limitations with webextensions): It seems like saving images is done by making a separate additional request for the file and then downloading it, rather than using the existing cached data. As a result, if the image file is deleted from the hosting server between being first viewed and then saved using this addon, it will instead download an empty file/404 error page contents into the filename (a common occurrence on sites like 4chan). Not sure if it's possible to get around this with the new API, but would be great if it could somehow default to the original cached data if available before attempting another download.