I bought something online and the tracking number a seller provides was 12 digit long? Help plz ASAP

That sounds about right, you can actually enter a tracking number into Google and it will identify the service it is for, or you can try entering it on the UPS site:

http://www.ups.com/tracking/tracking.htm...

My usps tracking number is 20 digits long, but it might be different for different kind of shipping service.

So try tracking the number in the usps website.

go to www.usps.com and enter the tracking number there to see if it's legit

Thanks to all the seller have me the 20 digit tracking # later that day but all answers were the best