What is a tracking number?
How to find your tracking number?
Track any package, freight and shipment
See Regular Expression patterns for Tracking numbers
I recently ran into the same need and have started an open source project called Argo: https://github.com/dsposito/argo
Argo determines the shipping carrier and provider (3rd party such as Endicia or Stamps.com) for a given tracking code.
A custom plushie I ordered back in December of 2023 was shipped at the beginning of Febuary and as of now I do not have any way of tracking the package. I've messaged the seller so I have yet to hear back. I hope it's not lost, I've ordered from her before with no issue. I'd hate to ask for a refund as it was over $100 and she spent a long time making the plushie. I've checked to make sure the address is correct and it is. Most likely I'll just have to let it go if I don't recieve it because it's not her fault but the carrier. Any tips would be appreciated :)