How to Read a USPS Tracking Number

Why USPS Tracking Numbers Look So Long

Most USPS tracking numbers are 20 to 22 digits long — far longer than a UPS or FedEx number. That's because USPS encodes a lot of information directly into the number: the service type, the mailer's ID, a unique serial number for the package, and a check digit to catch typos.

Once you understand the structure, a USPS tracking number stops looking like a random string and starts telling you exactly what it is.

The Two Main USPS Tracking Number Formats

1. Domestic: 20–22 digit numbers starting with 9

The vast majority of USPS tracking numbers you'll see are 20-digit strings that start with 9. The first few digits identify the mail service. Here are the most common:

For example, if your tracking number starts with 9400, you're most likely looking at a standard USPS Tracking or Priority Mail shipment. If it starts with 9205, it was sent Priority Mail Express — the fastest USPS domestic service.

2. International: Two letters + 9 digits + "US"

International USPS shipments use a completely different format based on the Universal Postal Union (UPU) standard. These are 13 characters total:

The two-letter prefix identifies the service type:

• EA, EB, EC, ED — Priority Mail Express International
• CP, CX — Priority Mail International
• LX, LC — First-Class Package International
• RX, RA, RB — Registered Mail International

The "US" suffix always appears at the end of outbound US shipments, confirming the origin country.

Breaking Down a Full USPS Tracking Number

Let's look at a typical domestic tracking number and what each section means:

• 94 — Application identifier (tells USPS systems this is a tracking barcode)
• 00 — Service type code (USPS Tracking)
• 111899 — Mailer ID (identifies the company or individual who sent it)
• 22339755731 — Serial number (unique to this specific package)
• 8 — Check digit (calculated from the other digits to catch scan errors)

You don't need to memorize these sections — the main takeaway is that the first 4 digits tell you the service, and the rest uniquely identify your package.

Where to Find Your USPS Tracking Number

Your USPS tracking number appears in several places:

• Order confirmation email — Most online retailers include it in the shipping notification email, usually labeled "Tracking Number" or "Track Your Order."
• USPS receipt — If you shipped at a Post Office counter, it's printed on your paper receipt.
• Shipping label — It's the long barcode number printed on the label attached to your package.
• USPS Informed Delivery — If you've signed up for this free service, USPS emails you a scan of incoming mail, sometimes before you receive the package.

What If My Tracking Number Isn't Working?

A few common reasons a USPS tracking number might not work:

• It's too new — Tracking information can take 12–24 hours to appear in USPS systems after a label is created.
• The number is incomplete — Make sure you copied all 20–22 digits. Missing even one digit will cause a lookup failure.
• Spaces and dashes — These are fine; TrackHive strips them automatically. "9400 1118 9922..." works the same as "9400111899..."
• Non-USPS number — Double-check your email. Some retailers use FedEx SmartPost or UPS SurePost, which use USPS for the last mile but may show a different carrier's number initially.

Tracking Multiple USPS Packages at Once

If you're waiting on several USPS shipments — common after holiday shopping or for small business owners managing returns — tracking them one by one is tedious. TrackHive's bulk tracking tool lets you paste up to 20 tracking numbers at once, regardless of carrier. USPS, FedEx, UPS, and DHL numbers can all go in the same batch.