USPS from ShipStation Guide | ShipEngine
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USPS from ShipStation
USPS from ShipStation offers domestic and international shipping services to ShipStation API accounts based in the US.
This guide provides developers with the details needed to build USPS from ShipStation shipping capabilities into your ShipStation API workflows.
ShipStation API also allows you to connect your own existing Stamps.com account to use the USPS services and rates available through that account in ShipStation API. The connection process and some usage details are different than those for USPS from ShipStation. For details about connecting and using your own Stamps.com account with ShipStation API, see our USPS (Stamps.com) Carrier Guide.
Requirements
carrier_name: stamps_com
- A ShipStation API account based in the US.
- ShipStation Carriers must be activated for the account and have a positive account balance to create labels. See our Using ShipStation Carriers page for details about activating it in your account.
- A weight value is required for all shipments.
Rates
USPS from ShipStation supports rate shopping with ShipStation API.
Service Details
The tables below provide the services available with USPS from ShipStation. Please note that carriers may update their available services at any time. To ensure you are always using valid services, you can use the list carrier services endpoint at any time.
USPS Domestic Services
| Service | Transit Time | Maximum Dimensions (LxWxH) | Max Weight | Service Code |
|---|---|---|---|---|
| USPS Ground Advantage* | 2-5 days | 22" x 18" x 15" | 70 lbs | usps_ground_advantage |
| USPS Priority Mail | 1-3 days | varies by package type | 70 lbs | usps_priority_mail |
| USPS Priority Mail Express | 1-2 days | L x 2xW x H cannot exceed 108" | 70 lbs | usps_priority_mail_express |
| Media Mail | 2-9 days | L x 2xW x H cannot exceed 108" | 70 lbs | usps_media_mail |
*In 2023, USPS Ground Advantage replaced both USPS First Class Package and Parcel Select Ground services.
Important: USPS International Shipping Updates
International Mail Service Suspensions - Effective: March 3, 2026
The Postal Service™ is temporarily suspending acceptance of items destined to the following countries, due to logistics impacts resulting from the conflict in the Middle East. Please refrain from mailing items addressed to the countries listed here until further notice:
Algeria, Armenia, Bahrain, Djibouti, Eritrea, Iran, Iraq, Israel, Kuwait, Libya, Madagascar, Oman, Pakistan, Qatar, Seychelles, Syria, Tanzania, United Arab Emirates
HS Codes Required
As of September 1, 2025, the U.S. Postal Service will require all international commercial shipments to include a six-digit Harmonized System (HS) code on customs declarations for each item, regardless of mail class. The HS code system, created by the World Customs Organization, is used by customs authorities worldwide to classify goods and assess tariffs. This update aligns USPS mailing standards with new Universal Postal Union (UPU) regulations, also taking effect Sept 1, requiring all member countries to enforce six-digit HS codes for commercial goods.
For a full list of Harmonization Codes, use the Harmonized Tariff Schedule search.
USPS International Services
| Service | Transit Time | Maximum Dimensions | Max Weight | Service Code |
|---|---|---|---|---|
| USPS First Class Mail Intl | 7-21 days | L x 2xW x H cannot exceed 136" | 64 oz | usps_first_class_mail_international |
| USPS Priority Mail Intl | 6-10 days | L x 2xW x H cannot exceed 108" | 70 lbs | usps_priority_mail_international |
| USPS Priority Mail Express Intl | 3-5 days | L x 2xW x H cannot exceed 108" | 70 lbs | usps_priority_mail_express_international |
NOTE: All international shipments using USPS First-Class Mail Int'l, Priority Mail Int'l, or Priority Express Int'l services will use Global Advantage Program labels by default.
GlobalPost Services
GlobalPost international services are also available under the USPS from ShipStation carrier, as USPS is the official first-mile carrier for GlobalPost shipments originating in the US.
| Service | Max Weight | Service Code |
|---|---|---|
| GlobalPost Economy Intl | 4.4 lbs | globalpost_economy |
| GlobalPost Standard Intl | 70 lbs | globalpost_priority |
| GlobalPost Plus | 66 lbs | gp_plus |
| GlobalPost SmartSaver Economy Intl | 4.4 lbs | globalpost_economy_smart_saver |
| GlobalPost SmartSaver Standard Intl | 70 lbs | globalpost_priority_smart_saver |
| GlobalPost Plus SmartSaver | 66 lbs | globalpost_plus |
Return Services
USPS from ShipStation supports return labels using any domestic services. Review the Return Shipping Labels page for details on creating return labels with ShipStation API.
Packages
The following carrier package types are available for USPS services:
| Package Name | API Code | Package Details |
|---|---|---|
| Medium Flat Rate Box | medium_flat_rate_box |
Domestic and international |
| Flat Rate Envelope | flat_rate_envelope |
Domestic and international |
| Small Flat Rate Box | small_flat_rate_box |
Domestic and international |
| Large Flat Rate Box | large_flat_rate_box |
Domestic and international |
| Flat Rate Padded Envelope | flat_rate_padded_envelope |
Domestic and international |
| Flat Rate Legal Envelope | flat_rate_legal_envelope |
Domestic and international |
Adding Shipment Insurance
USPS from ShipStation supports adding either carrier insurance or Parcelguard insurance (but not both) to shipments created with ShipStation API.
Review the Parcel Insurance page for details about adding shipment insurance with ShipStation API.
Label Support
- Label sizes: 4" x 6"
- Label formats: PDF, ZPL
Label Reference Fields
USPS from ShipStation supports adding custom label messages to all three label reference fields when using domestic services. International services do not support label messages.
Multi-Package Labels
USPS services do not support multi-package shipping labels at this time.
Label Branding
USPS from ShipStation supports adding a custom label image to your labels. See our Create Custom Shipping Labels page for details.
Voiding Labels
USPS supports voiding labels with ShipStation API, but it must be done within 28 days of label creation and the label cannot have been scanned by the USPS.
Paperless Labels
USPS from ShipStation supports paperless labels. This means you can generate a QR code for your customer and they can take that QR code to be scanned at participating USPS locations, who will then print the label for them.
Review our paperless labels page for details on how to generate a QR code instead of a printable label. Use the paperless value for the display_scheme property.
Customs Declarations
Customs declarations for GlobalPost and GAP labels are submitted to the carrier electronically. See our International Shipments page for details about shipping internationally via ShipStation API.
Delivery Confirmation
| Confirmation Type | API Code | Description |
|---|---|---|
| No confirmation | none |
Default. When no delivery confirmation is requested. |
| Delivery | delivery |
For general delivery confirmation. |
| Signature | signature |
A signature is required to complete the delivery. Not supported for international shipments. |
| Adult Signature | adult_signature |
An adult signature is required for the shipment to be delivered. |
| Restricted delivery | restricted_delivery |
Signature and Adult Signature confirmation types are not supported for international shipments.
See our Delivery Confirmation page for more details about using the confirmation property.
Advanced Options
USPS from ShipStation supports certain advanced options, which you can add to the shipment object when creating a shipment or label.
| Option | Name | Default Value | Description |
|---|---|---|---|
| Non Machinable | non_machinable |
false |
Indicates that the package cannot be processed through USPS sorting machines. |
To ensure you always have the most up-to-date information about a carrier's advanced options, use the list carrier options call.
Dangerous Goods
USPS from ShipStation does not support shipping dangerous goods.
Manifests
USPS from ShipStation supports creating manifests (called SCAN forms) via ShipStation API. If you plan to create a USPS SCAN form, you must manifest your day's shipments by 9pm local time.
See our Manifests page for more details about creating manifests with ShipStation API.
Scheduling Pickups
USPS from ShipStation supports scheduling pickups via ShipStation API. Pickups can only be scheduled one day in advance. For example, if you schedule a pickup on the 5th for the 7th, the pickup date scheduled by Stamps.com will be the 6th.
See our Schedule a Carrier Pickup page for more details about scheduling pickups using ShipStation API.
Service Points (PUDO)
USPS does not support shipping to service points.
Tracking
USPS from ShipStation supports receiving tracking updates. Review our Track a Package guides for details on tracking with the ShipStation API.