Ugh, I need this too, and it's nowhere to be found. I need to export some baners from artboards that meet specific file size, and I can't do that with anything else but save for web. Other saving methods don't support quality/weight change. If it's somehow in Export for screens I don't have it in my Photoshop CC... This is one of the lamest change for me.
It's simple... Go to > Windows tab (in illustrator) > Open Artboards tab > Click on the Artboard to be 'Save for Web' and that artboard only will be saved for web. Select from the layer (Artboards) to be exported one by one and 'Export for web'
In CC version you can use Quick Export as PNG option to export all Artboards at the same time. After you select all Artboards first, right click on it and then use Quick Export as PNG .
72 DPI? And that is intended to represent what now?
I haven't seen a 72 DPI monitor since the early 90s. I can't believe I can't tell illustrator the size in piexles, and then how large the canvas is. I am often designing something for a specific screen. I want that to print out in the correct size so we can quickly have a wall of screens for previews, but have the same file be pixel ready for the actual device. It's assuming ALL screens are 72 dpi. So if you give it 1280x800 (a common web starting point) then it assumes your size is 17.77 inches, and you can't change it. It seems like a pretty big mistake for Illustrator to only let you choose one set of units. It's either in inches (or cm if you're into that sort of thing) or in pixels. You can't have both.
I'm not saying I'm surprised. This is Adobe. If you weren't aware, they are always right.