USPS Tracking Codes: How to Read Every Format

USPS tracking codes come in two main forms: a 22-digit domestic number that usually starts with 92, 93, 94 or 95, and a 13-character international code such as EC 123 456 789 US. In a domestic code, the first two digits show how the label was created, not which mail service was used; the service is encoded in the three digits that follow.

That second point trips up a lot of people. Older guides say “94 means Ground Advantage” or “92 means Priority Mail,” but USPS’s own barcode specification says otherwise. This guide explains how to read each part of a USPS tracking code, which formats you’ll see, and what to do when one won’t track.

What Are USPS Tracking Codes?

A USPS tracking code is the unique number printed under the barcode on a trackable USPS label. It lets USPS, the sender and the recipient look up every scan the item gets, from acceptance through delivery, at USPS.com, in the USPS app or by text. Our complete guide to USPS tracking covers the lookup tools themselves.

Domestic package labels use the Intelligent Mail package barcode (IMpb), which USPS defines in Publication 199. The barcode holds a routing ZIP Code plus the tracking number, but only the tracking number is printed in human-readable form beneath it. International items use the Universal Postal Union’s S10 format instead, which is why they look completely different.

Tracking is a separate feature from the delivery speed you pay for. Ground Advantage, Priority Mail and Priority Mail Express all include USPS Tracking, while First-Class Mail letters and flats don’t unless you add an extra service. If you’re comparing services by speed, our page on expedited shipping options lays out the 2–3 day choices across carriers.

How Do You Read a 22-Digit USPS Tracking Code?

Every domestic IMpb tracking number contains the same building blocks, in this order: a channel application identifier, a service type code, the mailer’s ID, a serial number and a check digit. USPS Publication 199 lists those five elements as the parts of the tracking number.

The routing part of the barcode, the GS1 identifier “420” followed by the destination ZIP Code, is hidden from the printed number. That’s why the digits you type into USPS Tracking are shorter than the full barcode a scanner reads.

What do the first two digits of a USPS tracking code mean?

The first two digits are the channel application identifier, and they describe the payment channel rather than the service. According to Publication 199, the current values are:

• 92: a commercial mailer with a nine-digit Mailer ID
• 93: a commercial mailer with a six-digit Mailer ID
• 94: USPS APIs, PC Postage vendors and postage meters
• 95: USPS Retail counters and self-service kiosks

So a Priority Mail package bought at a Post Office counter and one printed through an online shipping platform can carry codes that start differently. Our page on what a USPS tracking number starts with goes deeper into specific prefixes, and the tracking results page at USPS.com always names the actual service.

What USPS Tracking Code Formats Will You See?

USPS publishes sample formats for each trackable service. The table below uses those samples, with zeros standing in for the unique digits. Remember that the leading digits shift with the label channel, so treat the prefixes as examples rather than fixed rules.

Some longer domestic codes exist too. Publication 199 allows serial numbers of several lengths, so business shippers with certain Mailer IDs produce tracking numbers longer than 22 digits. They track the same way at USPS.com.

What do the letters in an international USPS tracking code mean?

International codes follow the UPU S10 standard: two service letters, eight serial digits, one check digit and a two-letter country code. The closing “US” means the item was mailed in the United States, and the first letter hints at the product: E for express items such as Priority Mail Express International, C for parcels such as Priority Mail International, R for registered items, and L for tracked small packets.

Once an international item leaves the U.S., the destination country’s postal service adds its own scans to the same code. For how those handoffs show up and which sites to check, see our guide to USPS tracking international shipments.

Where Do You Find Your USPS Tracking Code?

The code is printed directly below the barcode on the label, on the Post Office receipt if you paid at the counter, and in the order history or confirmation email if you bought postage online. Our step-by-step guide to finding a USPS tracking number from receipt paperwork shows exactly which line on the slip to read.

• Shipping label: the human-readable digits under the barcode. If you print your own shipping labels, the code is also saved in the account you bought them from.
• Post Office receipt: listed next to the service you bought, usually as the USPS Tracking number.
• Online order or email: retailers and shipping platforms include the code in shipping confirmations.
• Informed Delivery: if you’re enrolled, incoming packages addressed to you appear on the dashboard with their codes.

Read the code under the barcode, not other numbers on the label such as a ZIP routing code, order number or Mailer ID. If you are the recipient and never saw the label, the sender or retailer is the best source for the code.

What Should You Do When a USPS Tracking Code Won’t Track?

Most failures come from a typo, a label that hasn’t been scanned yet, or a number that isn’t a tracking code at all. The check digit means a single mistyped digit almost always returns no result, so start there.

1. Copy, don’t retype. Paste the code without spaces or dashes, and check look-alike characters in international codes (O and 0, I and 1).
2. Check the length. A domestic code should be 22 digits (sometimes more), and an international one 13 characters ending in two letters.
3. Give it time. A label creates a record right away, but the first real scan comes only when USPS accepts the package.
4. Ask the sender. If you’re the recipient, the sender can confirm the full code and when the package was handed over.
5. Escalate after 7 days. USPS lets you submit a Missing Mail search starting 7 days after the mailing date.

If USPS returns a status message instead of scans, our guide explains what USPS tracking not available means and how to search again correctly. If you need a person to help, the USPS tracking support page lists the contact routes. General customer support basics apply too: have the code, mailing date and addresses ready before you call.

How Long Does a USPS Tracking Code Stay Active?

USPS keeps standard tracking history for 120 days, after which a code stops returning results at USPS.com. That lines up with the IMpb rule that a domestic serial number must stay unique for 120 days, after which the same number can eventually be reused by the same mailer.

Businesses that need proof of delivery for longer can buy USPS Tracking Plus, which extends how long scan and signature records are kept. If a code shows an old delivery from months ago, it may be a recycled number or a scam, so confirm with the sender. Our guide to package tracking services explains how carrier scan records work across companies, and you can follow non-USPS shipments in UPS tracking.

How Do You Get USPS Tracking Codes When You Ship?

Every trackable USPS label you buy comes with a code automatically. Online shippers get theirs the moment the label is created, which you can share with the recipient before the package is even dropped off.

ParcelPath is a free way to create USPS and UPS labels, with no subscription, per-label fees or minimums, and up to 89% off USPS and 85% off UPS. Each label carries a standard USPS tracking code that works at USPS.com and in the USPS app. You can compare live USPS rates for your package in the rate calculator, see more on the ParcelPath shipping calculator page, and read about discounted shipping for online stores or connecting e-commerce platforms and shipping integrations.

Frequently Asked Questions

How many digits are in a USPS tracking code?

Most domestic USPS tracking codes are 22 digits long, though some business shippers’ codes run longer because USPS allows several serial-number lengths. International codes are 13 characters: two letters, nine digits and a two-letter country code such as US. Global Express Guaranteed uses a 10-digit number.

Does a USPS tracking code starting with 94 mean Ground Advantage?

No. In USPS Publication 199, the first two digits are a channel identifier: 92 and 93 are commercial mailers, 94 is online postage, APIs and meters, and 95 is Post Office retail and kiosks. The mail class is encoded in the next three digits, the service type code, and USPS.com shows the actual service.

What does “US” at the end of a USPS tracking code mean?

The “US” suffix is the country code of the postal service that accepted the item, under the Universal Postal Union’s S10 standard. It means the package was mailed in the United States. The two letters at the start identify the product type, such as E for express items and C for parcels.

Can two packages have the same USPS tracking code?

Not at the same time. USPS requires each domestic serial number to stay unique for 120 days, which matches how long standard tracking history is kept. After that window a number can eventually be reused, so if a code shows a delivery from months ago, check with the sender before trusting it.

Why does my USPS tracking code say it’s invalid?

Usually because a digit was mistyped. The last digit of every USPS tracking code is a MOD 10 check digit, so one wrong number makes the whole code fail. Paste the code without spaces, confirm it’s 22 digits or 13 characters, and ask the sender to resend it if the problem persists.

Sources

• USPS Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide (PostalPro); channel identifier 95 per the July 2025 edition (v33)
• USPS FAQ: USPS Tracking, The Basics
• USPS FAQ: How to find your tracking number
• USPS: Missing Mail and Lost Packages
• S10 (UPU standard) tracking identifiers

Part of our USPS Tracking guide. Related: USPS Tracking and Delivery, USPS Tracking Not Updating, USPS Tracking Not Updating After Drop Off.