In another comment I mentioned I use nanoid in my projects now. It has a default space of 64^21 and has an a page where you can play with key lengths and alpha

In another comment I mentioned I use nanoid in my projects now. It has a default space of 64^21 and has an a page where you can play with key lengths and alphabet sizes and see the probability of collisions : https://zelark.github.io/nano-id-cc/ https://zelark.github.io/nano-id-cc/ At the default 64 character alphabet with a 21 character key length it would take ~41 million years in order to have a 1% probability of at least one collision if you generated 1000 ids per second.