Eventually I’m sure they do. They’re not meant to be unique forever and many of the digits carry other information, so aren’t able to be incremented.

All carriers let their tracking numbers expire, so the numbers don’t mean anything after a while and I would imagine they’re eventually put back in the pool sometime after that expiration.

I just checked a package that was shipped with Fedex.

Tracking number is 781687472471705 so it could possibly be 999999999999999

So Fedex could deliver 142,857 packages to every person on earth and not run out of numbers.

The number is probably generated by some sort of HASH that takes into account order number and date and a few other factors which would pretty much guarantee there is never a collision.

There’s other information in the tracking number, so not all digits are open to be incremented.

I’m most familiar with UPS, and with a tracking number you can tell the service level, the shipper, and probably some other information. Wikipedia says only the last 8 digits are package identifiers. So you’re only looking at 100 million numbers.

https://en.wikipedia.org/wiki/Tracking_number

A quick reading of the international standard used by USPS looks like they have 8 digits for package identification as well. So again, 100 million possibilities.

https://en.wikipedia.org/wiki/S10_(UPU_standard)

They’d have to be recycled.

I order a ton of shit from Newegg and it all went from the same warehouse to my house. There isn’t a pattern in the numbers. (at least with FedEX)

I did check UPS and there are patterns. And something ordered about two years ago isn’t registered in their system. My really old Fedex tracking numbers still work.