USPS (Stamps.com) Carrier Guide
Stamps.com with ShipEngine provides access to USPS domestic and international shipping services for packages originating in the United States.
This guide provides developers the details needed to build USPS shipping capabilities using a Stamps.com account into your ShipEngine workflows.
Requirements
Property | Type | Required? |
---|---|---|
username | string | required |
password | string | required |
Connect Account
You can connect a Stamps.com account using the POST method to the /v1/conections/carriers/
endpoint, or via the ShipEngine Dashboard.
For instructions on connecting a Stamps.com via the ShipEngine dashboard, go to our Stamps.com help article.
Connect via Endpoint
carrier_name
: stamps_com
POST /v1/connections/carriers/:carrier_name
A successful connection will return a response with the carrier_id
, which you'll use for any requests for this account going forward.
Rates
Use the rates endpoint to fetch estimated rates for Stamps.com-provided services. See our Calculate Shipping Costs page for details about rate shopping with ShipEngine.
Service Details
Available Stamps.com services are provided below, which include both USPS and GlobalPost services. 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.
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 |
GlobalPost Services
For all GlobalPost services, transit time will vary depending on the destination country.
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
Stamps.com supports returns using any domestic service. Review the Return Shipping Labels page for details on creating return labels with ShipEngine.
Packages
The following carrier package types are available for CarrierName 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
Stamps.com supports adding carrier insurance to your shipments.
Review the Parcel Insurance page for details on adding shipment insurance with ShipEngine.
Label Support
- Label sizes: 4" x 6"
- Label formats: PDF, ZPL
Label Reference Fields
Label messages are supported for domestic shipments only. You can use all three label reference fields.
Multi-Package Labels
USPS does not support multi-package shipments at this time.
Label Branding
Stamps.com supports adding a custom label image to your labels. See our Create Custom Shipping Labels page for details.
Voiding Labels
Stamps.com supports voiding labels using ShipEngine, but it must be done within 28 days of label creation.
See our Void a Label page for details about voiding labels with ShipEngine.
Paperless Labels
USPS supports paperless labels with their services. 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. Currently this supports the qr_code
value for the display_scheme
property.
Example QR Code

Customer Communications
Using paperless labels might be a new experience for your customers. The USPS suggests sending out an email with the QR code label to help educate your customer on what they need to do to ship their package.
The email containing the QR Code should also include instructions on how to find participating USPS Post Offices by visiting https://tools.usps.com/find-location.htm?locationType=po&serviceType=lbroretail&address=18702, where the value of the address parameter is customer's ZIP Code (such as 18702 in this example). The USPS Retail Associate at that location's Retail Counter will scan the QR Code and print the shipping label, affix it to the package, and provide a receipt.
If the customer has access to a printer, they may choose instead to print the label directly at https://tools.usps.com/label-broker.htm?LabelID=XYZZYPJK&zip=18702, where XYZZYPJK is the Label ID returned by ShipEngine, and 18702 is the ship_from
postal_code
.
Customs Declarations
Customs declarations for GlobalPost and GAP labels are submitted to the carrier electronically. See our International Shipments page for details about shpping internationally via ShipEngine.
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. |
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
Stamps.com 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. |
Dangerous Goods | dangerous_goods | false | Indicates this shipment contains dangerous goods |
To ensure you always have the most up-to-date information about a carrier's advanced options, use the list carrier options call.
Manifests
USPS supports creating manifests (called SCAN forms) via ShipEngine. 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 ShipEngine.
Scheduling Pickups
USPS supports scheduling pickups via ShipEngine. 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 ShipEngine.
Service Points (PUDO)
USPS does not support shipping to service points.
Tracking
ShipEngine's integration with Stamps.com supports receiving tracking updates. Review our ​Track a Package guides​​ for details on tracking with the ShipEngine API.
Disconnecting Your Stamps.com Account
See the Disconnect section in our Delete a Carrier page for the process of deleting or disconnecting a carrier from ShipEngine.