Is it safe to turn a UUID into a short code? (only use first 8 chars)

Question

We use UUIDs for our primary keys in our db (generated by php, stored in mysql). The problem is that when someone wants to edit something or view their profile, they have this huge, scary, ugly uuid string at the end of the url. (edit?id=.....)

Would it be safe (read: still unique) if we only used the first 8 characters, everything before the first hyphen?

If it is NOT safe, is there some way to translate it into something else shorter for use in the url that could be translated back into the hex to use as a lookup? I know that I can base64 encode it to bring it down to 22 characters, but is there something even shorter?

EDIT I have read this question and it said to use base64. again, anything shorter?

Answer 1

Shortening the UUID increases the probability of a collision. You can do it, but it's a bad idea. Using only 8 characters means just 4 bytes of data, so you'd expect a collision once you have about 2^16 IDs - far from ideal.

Your best option is to take the raw bytes of the UUID (not the hex representation) and encode it using base64. Or, just don't worry much, because I seriously doubt your users care what's in the URL.