Dave here from the Guru Team :)
When looking to print labels through Shopify we actually have some recommended printers which are:
We also have this great doc for more information with regards to printers and shipping labels which you may find useful :)
I hope this helps!
All the Best,
Dave | Shopify
UPS API sends labels in the following format :
Thermal or Zebra printers can print labels in both these formats. Although ZPL is the default format.
Shopify converts these labels into PDF and the following printers can be used to print these labels :
Dymo LabelWriter 4XL
However, if you have a printer that only recognises PNG, you can use the multi carrier shipping label app to generate the labels in this format and print them.