Get your USPS Web Tools credentials First of all, having an account on USPS Web Tools is crucial. Kindly create a new one if you haven’t registered:

https://www.mageplaza.com/kb/how-to-configure-usps-carrier-magento-2.html Configuring United States Postal Service (USPS) Carier allows you to offer the domestic and intertional shipping services on ground or airway conveniently. This is the service of United States goverment. Thus, what credentials you need to connect your Magento 2 store to the USPS server. Let check it out...