They’re short unique strings:

Sqids (pronounced “squids”) is an open-source library that lets you generate YouTube-looking IDs from numbers. These IDs are short, can be generated from a custom alphabet and are guaranteed to be collision-free.

I haven’t dug into the details enough to know how they can be guaranteed to be collision-free.

As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.

Read my blog posting guidelines here.