Most USPS tracking numbers are 20 or 22 digits long. International parcels may instead use a 13-character code ending in “US”, which follows the worldwide UPU S10 format.
In this guide:
- USPS tracking number formats at a glance
- How to read a USPS tracking number
- What if your number looks different?
- What the first digits tell you
The length depends on the service used. The good news: you do not need to memorise the formats — just enter the complete number exactly as printed on your receipt or label, and the tracking system will recognise it.
USPS tracking number formats at a glance
| Length | Example pattern | Used for |
|---|---|---|
| 22 digits | Starts with 94 | Ground Advantage, Priority Mail, most domestic parcels |
| 20 digits | Varies | Some domestic and older services |
| 13 characters | Ends with US | International registered and EMS items (UPU S10) |
The 22-digit format starting with 94 is by far the most common today. If your number looks like 9400 11xx xxxx xxxx xxxx xx, it is a standard modern USPS tracking number — enter all 22 digits with no spaces.
How to read a USPS tracking number
The first few digits identify the service: numbers starting with 9400, 9407 or 9434 are typical of Ground Advantage and Priority Mail, while 9205 or 9270 often belong to Priority Mail Express. The remaining digits are your unique package identifier plus a check digit. You do not need to decode any of this to track — it is just useful for spotting typos.
What if your number looks different?
If your code is shorter than 20 digits, double-check that you copied the whole thing — receipts sometimes wrap the number across two lines. Marketplace sellers occasionally send an order number instead of a tracking number by mistake; if tracking returns no result, ask the seller to confirm the USPS tracking code. You can try any complete number in the search box on our couriers page.
What the first digits tell you
The opening digits of a USPS tracking number identify the mail class. Numbers starting with 9400 or 9407 usually belong to Ground Advantage or Priority Mail, 9270 or 9205 often indicate Priority Mail Express, and 9401 can appear on certified mail. International S10 codes use two-letter service prefixes such as CP, EM or RA before the nine digits and the US suffix. This is only a rough guide — the definitive answer always comes from entering the number into tracking.
Are USPS tracking numbers always 22 digits?
No. While 22 digits is the most common modern format, 20-digit numbers and 13-character international codes are also valid USPS tracking numbers.
Do USPS tracking numbers contain letters?
Domestic USPS tracking numbers are digits only. If your code contains letters and ends in “US”, it is an international UPU S10 number — enter it exactly as printed, letters included.
Can two packages have the same tracking number?
No. USPS tracking numbers are unique to each shipment, so your number identifies only your parcel.
Where is the tracking number on my receipt?
On a post office receipt it is printed near the bottom, labelled as the tracking or label number. On online labels it appears on the confirmation page and in the shipping email.