USPS
Navigate to WooCommerce → ShipLabel → USPS.
| Setting | Default | Description |
|---|---|---|
| Enabled | Off | Master toggle for USPS label generation and checkout rates |
| Environment | Production | Production or Sandbox / Testing |
| Client ID | - | USPS OAuth 2.0 client ID from developers.usps.com |
| Client Secret | - | USPS OAuth 2.0 client secret |
| Default service | Priority Mail | Pre-selected service on the order panel |
| Label format | PDF or TIFF |
Click Test Connection after entering credentials to confirm ShipLabel can fetch an OAuth token from USPS.
A USPS developer account is free at developers.usps.com (opens in a new tab). Use the Sandbox / Testing environment to generate test labels before going live.
Supported Services
USPS Priority Mail, Priority Mail Express, Ground Advantage, First-Class Package, Media Mail, and Library Mail.
Package-Type Validation
Flat Rate packaging (envelope or box) is only offered on Priority Mail and Priority Mail Express (Express: envelope only). The order panel disables Flat Rate options that don't apply to the selected service, and ShipLabel double-checks the combination server-side before contacting USPS, so you get a plain-English explanation instead of a rejected label purchase.