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How To Decode USPS Tracking Numbers

This article highlights how USPS tracking numbers are structured and what each section means

USPS tracking numbers are not random. Each number follows a defined structure that contains important information about the shipment, including the service type, the mailer, and a built-in validation digit.

Understanding how a USPS tracking number is formatted can help operations teams troubleshoot delivery issues, validate shipments, and better interpret tracking data across systems. This is especially valuable for high-volume shippers and 3PLs managing multiple carriers and service levels.

USPS Tracking Number Breakdown

Below is a breakdown of how each segment of a USPS tracking number is structured and what it represents.

Example Tracking Number: 
9241990109329603875894

92    419  901093296    0387589  4
Postal Code Service Type Mailer ID Sequence Number Check Digit

A standard USPS tracking number is made up of multiple segments, each serving a specific purpose in identifying and validating a shipment.

  • Postal Code (First 2 Digits): The first two digits identify the carrier. For USPS shipments, this is typically 92, 93, 94, or 95, depending on the service and format. This prefix ensures the tracking number is routed correctly within carrier systems and integrations.

  • Service Type (Next 3 Digits): The next three digits indicate the USPS service used for the shipment, such as the below. Each service type maps to a specific code, allowing systems to determine expected delivery speeds, pricing structures, and service rules.

    • Priority Mail

    • First-Class Package

    • Parcel Select

    • Certified Mail

  • Mailer ID (Next 6–9 Digits): The Mailer ID identifies the shipper or organization that generated the label. This segment is critical for:

    • Tracking shipment ownership

    • Reconciling billing

    • Monitoring performance by client or account

  • Sequence Number (Next 6–8 Digits): This portion is a unique identifier assigned to each individual package within the mailer’s account. It ensures that every shipment can be distinguished, even when processed in high-volume batch environments.

  • Check Digit (Final Digit): The final digit is a validation number calculated using the rest of the tracking number. Its purpose is to:

    • Verify the tracking number is correctly formatted

    • Prevent errors during data entry or system transmission

    • Ensure integrity across carrier and software systems

                                                         

 

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