OLL 18
The algorithm, how to recognise it and how to practise it without cheating.
Probability1/54
Moves13
TypeDot
Inverse and mirror—
Recommended algorithm
r U R' U R U2 r2 U' R U' R' U2 r13 moves
How to recognise it
A dot with two adjacent corners yellow on top. Hold them at the back: the front side shows a full yellow bar.
Its inverse is another case
Do the 18 algorithm backwards, r' U2 R U R' U r2 U2 R' U' R U' r', and you are solving 19.
That's why CubeDojo never scrambles 18 that way: it builds a random state with the case fixed, so you practise 18 and not 19.
Practise 18 now
Random-state scrambles, a timer and spaced review. Free, on the web and on your phone.