I recently started to look at Nikoli's records of how other people have solved sudoku.
What I've noticed is that some of the very fast solvers are using techniques that I definitely don't have!
They are placing numbers that I can't place, or see how they can be placed, until (much) later in the puzzle - and they're doing it fast
I'd like to talk you through some of these...
One example comes from the Sudoku on Nov 14https://member.nikoli.com/play/about/6657.html
Looking at speedy Hideaki Jo's solution - click on his time, 2:06
(Unfortunately I think you need to be logged into Nikoli to see this - I would prefer to use a public site if anyone knows of one that provides puzzle walkthrus)
I can see how the first two 7s are placed, but then the next 2? I understand the 2 is in this column but why is it in that row: it doesn't seem to immediately follow... but H.Jo seems confident in placing it after a couple of seconds and is correct about it.
This doesn't seem to be the natural next placement, I think it shows that H.Jo has a different technique to mine.
This might be a trivial miss on my part... but there are several more examples of this
If I get some interest I will add more to this thread