mattmiller wrote: ↑
Wed Sep 11, 2019 5:19 pm
Also, you'll find lots of articles saying you need level-shifters to drive them but I've never done so and not had a problem
It usually works but there is no guarantee. You're violating the published specifications of the WS2812 if you do this. The datasheet says input high is 0.7 x Vdd which means > 3.5V is considered high if you power it via 5V. Feeding it 3.3V from the Pi means you're in the undefined region between input high and input low.
If it is for a one-off home project then skip the level shifter. If you're making it to sell or it'll be installed somewhere difficult to access then put the level shifter in for peace of mind.