Are preorders necessary on Amazon?

There’s a myth that if people preorder your book, Amazon is more likely to print and promote paperback copies —  this is false!

They have no impact on how many copies Amazon prints — by using Amazon, you ensure that they will “print on demand” every single copy that is ordered. That is their policy.

There is an option to make your book available for pre-order on KDP — you will see it at the end of the publishing steps. I don’t think it’s necessary for most people, but you of course can do it if you’d like! 

It is helpful to make sure that your network / audience buys your book early on after the launch, but there's no difference whether they buy shortly after you launch, or via a preorder.