How to make i3wm statusbar transparent?

You can make the bar transparent, but you can't make the background of the bar transparent. I'm working on it though, the question is just whether it will be merged... :)

for id in `xwininfo -all -root | grep 'i3bar for output' | sed 's#\s\+# #g' | cut -d " " -f2`; do transset -i $id > /dev/null; done

That's not what I mean. You can only set the overall i3bar transparency. If you want the background to be completely transparent, text to be 50% transparent and workspace icons to be 25% transparent, you're hitting a wall. In the compositor you cannot reference individual elements.

FYI, i3-gaps now supports i3bar transparency using RGBA colors. In i3 this isn't possible due to a few very annoying reasons like cairo bugs.