[Reason077]

My old MacBook Air did this a lot! My 2017 13" MacBook Pro does it too, but it's intermittent and much less noticeable. In both cases it completely disappears if you unplug the AC.

[LyndsySimon]

Ditto. I had a late-2013 15” MBP that did it consistently, and it was worse when you touched the bottom of the chassis. My mid-2015 MBP did it slightly, and I’ve not detected it on my current-gen 13” MBP or any of my non-Apple hardware.

[Reason077]

It's noticeable on my 13" 2017 non-touchbar MacBook Pro, but only when you run your fingers along the part of the case above the keyboard.

It was much more noticeable on the MacBook Air, with pretty much the entire aluminium surface of the case having the issue.

[ksec]

I didn't notice it when I had the 2017 Macbook, but both my Macbook Air and MBP 2015 has the same issue. Why hasnt Apple solve this after all these years?

Edit, I am using it with the UK plug, unsure how this is a grounding issue.

[Reason077]

I'm pretty sure the UK MacBook charger plug is not grounded. It has the ground pin, of course (UK sockets won't accept a plug without it), but there's only the standard 2 wires going from the detachable plug to the main body of the charger.