PLL Ub
The algorithm, how to recognise it and how to practise it without cheating.
Recommended algorithm
M2 U' M U2 M' U' M211 moves
Alternatives
R2 U R U R' U' R' U' R' U R'11 moves · R and U only
How to recognise it
One side has a full bar and the other three have headlights: hold the bar at the back. The front edge has the colour of the left side's headlights.
Its inverse is another case
Do the Ub algorithm backwards, M2 U M U2 M' U M2, and you are solving Ua.
That's why CubeDojo never scrambles Ub that way: it builds a random state with the case fixed, so you practise Ub and not Ua.
Practise Ub now
Random-state scrambles, a timer and spaced review. Free, on the web and on your phone.