OLL 50
The algorithm, how to recognise it and how to practise it without cheating.
Recommended algorithm
r' U r2 U' r2 U' r2 U r'9 moves
How to recognise it
Only the right and front edges are yellow on top. A full yellow bar on the left, and the back-right corner's yellow faces back.
Its inverse is another case
Do the 50 algorithm backwards, r U' r2 U r2 U r2 U' r, and you are solving 49.
That's why CubeDojo never scrambles 50 that way: it builds a random state with the case fixed, so you practise 50 and not 49.
Practise 50 now
Random-state scrambles, a timer and spaced review. Free, on the web and on your phone.