En el artículo , Tim+ escribió:
It depends on the browser the end user is using.
dl=1 tells the browser the URL is a download link. Here on Firefox on Win7 it correctly presents a "save as" dialog. dl=0 displays the image in a browser tab.
I think you said you're using a phone. Downloading may not be relevant in that context so with dl=1 the browser probably defaults to displaying the image as popping up a save dialog wouldn't be appropriate.