OSM Guide

OSM provides data-driven domestic and international shipping services. They partner with USPS for last-mile delivery on all domestic packages. By combining their expertise with the extensive coverage of USPS, they can provide greater efficiency and accuracy – and a lower total cost of shipping for any business.

This guide provides detailed information on utilizing OSM shipping with the EasyPost API, focusing on account setup, rates, label creation, manifests, tracking, and more.


Account Registration

Sign up for an EasyPost account to obtain a Test and Production API key. See Authentication and Key Management for more information.

Note: Negotiated rates are only available in Production mode.

Please review the Getting Started Guide for more information.

Carrier Setup

Upon sign-up with EasyPost, users gain immediate access to Default Carrier Accounts, which can be enabled directly from the Dashboard. For additional carriers, EasyPost supports a Bring Your Own Account (BYOA) option. This requires users to register directly with the respective carrier.

OSM Shipper Account Registration

  1. Complete registration on the OSM website. Once registered, an OSM representative will be in touch for additional details regarding the account.

  2. Inform OSM about using EasyPost's API for label purchases.

  3. Obtain the following account credentials from OSM:

    1. Account Number
    2. Mailer ID
    3. Facility Code/Cost Center ID (optional)
    4. Company Name
    5. SFTP Account
  4. Input carrier-specific credentials within the EasyPost Carrier Account Dashboard for comprehensive rate access.

OSM Account via API

The API structure specified by EasyPost can also be used to add the OSM carrier shipper account.

curl -X POST https://api.easypost.com/v2/carrier_accounts \
  -H 'Content-Type: application/json' \
  -d '{
  "type": "OsmWorldwideAccount",
  "description": "OsmWorldwideAccount",
  "carrier_account": {
    "credentials": {
      "account_number": "VALUE",
      "aws_sftp_username": "VALUE",
      "company_name": "VALUE",
      "facility_code": "VALUE",
      "mailer_id": "VALUE"

Software Requirements

Download an EasyPost Client Library or utilize the REST API with cURL.

Documentation Review

Examine the EasyPost Objects section to understand the API's structure, which is critical for constructing requests and interpreting responses.


When integrating an OSM account with EasyPost, users should be aware of how rates are managed and displayed. Here's a breakdown of key points:

Default Rate Display

  • EasyPost initially returns a one cent rate for shipments once the OSM account is set up.
  • OSM will charge the appropriate amount for postage via their billing system.

Rate Card

  • OSM Worldwide representatives provide rate cards detailing expected costs based on shipment parameters (package size, weight, location, etc.) .
  • Acquiring this custom rate card from OSM is crucial, as EasyPost is not automatically privy to these rates.

Rate Card Integration

Once the rate card is received from OSM, users should contact our Support team for assistance installing this rate card to their account.

Service Levels

OSM delivers 6 days per week (Mon-Sat). The service levels through EasyPost include:

Transit Time
Max Dimensions (inches)
Max Weight (ounces)

Predefined Packages

OSM has a few predefined packages supported by EasyPost. Predefined packages are an easy way to classify and price a package.

  • Types: parcel, irregularparcel, softpack
  • Usage: Specify in EasyPost API request for rate retrieval.

Generating Shipping Labels

With EasyPost, the process for generating shipping labels for OSM is the same as generating them for any other carrier.

Review the Getting Started Guide for help generating a shipping label.

Supported Options

Label Formats and Sizes

  • ZPL Format Requirement
    • Labels submitted to OSM for validation during onboarding must be exclusively in ZPL format.
    • Conversion to or from other formats is not supported and will result in failure.
  • Recommended Printer Models
    • OSM Worldwide recommends using Zebra Models S4M and GK420d.
  • Supported Label Size
    • OSM supports a 4 x 6 label size.

Advanced Options and Returns

  • Return Label Support
    • Return label types are supported by OSM.
    • A separate service level is available specifically for returns.
  • Pricing for Returns
    • Return services are offered at discounted rates compared to standard ground service levels.
  • Rating and Purchasing Returns
    • No unique rules are required for rating and purchasing a return label with OSM.

Hazardous Materials (HAZMAT)

For safety reasons, most hazardous materials are non-mailable. However, some hazardous materials and otherwise restricted matter, or perishable matter are permitted to be mailed when the requirements of the USPS are met.

OSM Worldwide follows USPS guidelines for shipping hazardous materials. For a list of items and definitions of other terms that relate to hazardous materials, refer to the USPS Hazardous Materials Guidelines.

See the EasyPost USPS Guide for detailed information on shipping restrictions, labeling requirements, transportation, and more.


Manifesting is both supported and required for all label purchases with OSM.

  • Manifesting Timeline
    • Shipments purchased over 120 days ago are archived by OSM and cannot be manifested.
    • Labels purchased up to 119 days ago are eligible for manifesting, but it is not recommended.

It is advisable to manifest shipment labels within 10 days of purchase for optimal processing and compliance with OSM guidelines.


OSM supports pickups at the customer's facility.

  • Customer Agreement
    • Pickup services are available to any customer based on their specific agreement with OSM.
  • Arrangement and Limitations
    • Regular pickups can be arranged directly with the OSM team during the registration process.
    • Pickups CANNOT be scheduled through the EasyPost API.


EasyPost simplifies package tracking by offering two methods:

  • Tracking with an existing number and carrier.
  • Using a Tracker included with an EasyPost-purchased shipping label.

The service integrates webhooks for timely shipment updates. For detailed information on tracking methods, visit the Tracking Guide.

Additional Resources

Carrier Metadata

The Carrier Metadata endpoint can programmatically return information about OSM service levels, predefined packages, supported features, and shipment options.

Use this information to quickly integrate with OSM and make educated decisions about the mix of carriers for shipping needs. Additionally, the Carrier Metadata endpoint is available to retrieve comprehensive information about all carriers on the EasyPost platform, enhancing decision-making for carrier services.

Support and Troubleshooting

In addition to the guidance provided in our Carrier Guides, EasyPost offers support to assist with FAQs, troubleshooting issues, and inquiries related to the EasyPost platform.

Please visit the Help Center for more information.

Talk to a Shipping Expert

For questions about getting started with OSM through the EasyPost API please talk to a Shipping Expert or contact our Support team.