The difference at a glance
| Code | Stands for | Serves |
|---|---|---|
| APO | Army Post Office | Army and Air Force units |
| FPO | Fleet Post Office | Navy and Marine Corps units and ships |
| DPO | Diplomatic Post Office | U.S. embassies and consulates |
On a label, each one takes the place of the city. The rest of the address, a name, a unit and box, a region code and a ZIP, is the same for all three.
The ZIP decides which one to use
You can’t choose between APO, FPO and DPO by the recipient’s branch of service. USPS assigns every military ZIP to exactly one of the three, and the designation on the label has to match. The ZIP 09021, for example, is an APO. The ZIP 09618 is an FPO. The ZIP 09498 is a DPO.
Of the 557 ZIPs USPS lists as active, this site has a type on file for all but 13. 197 are APO, 186 are FPO and 161 are DPO. Every ZIP has its own page in the ZIP code list showing the type and how sure we are of it.
Why mix-ups happen
- People assume by branch. Branch is a rough guide, but USPS assigns the designation to the ZIP. The ZIP is what counts.
- Designations change. USPS publishes change notices in its Postal Bulletin, and a ZIP that was once FPO can turn up later as DPO or APO. Old address books go stale.
- Shipping software is strict. Address checks treat APO, FPO and DPO as the city name, so a mismatch can be rejected or rewritten.
How to tell which one a ZIP is
Paste the full address into the address checker. It compares the post office on the label with USPS’s assignment for the ZIP and tells you how strong the evidence is. When USPS has published a recent change notice for the ZIP, a mismatch is flagged as a problem. When the evidence is older, it’s flagged as a warning, with wording that matches how sure the data is.
The safest source is the recipient, who has the address they were issued. Use the checker to catch typos and mix-ups, not to override what they tell you.
Questions about APO, FPO and DPO
Is APO or FPO for the Navy?
FPO (Fleet Post Office) serves Navy and Marine Corps units and ships. APO serves Army and Air Force units. But the ZIP decides which one goes on the label, so check the ZIP rather than assuming from the branch.
Can I use APO instead of FPO if the ZIP is the same?
No. USPS assigns each ZIP to exactly one of APO, FPO or DPO. Writing the wrong one can make USPS address checks and shipping software reject or rewrite the address.
Do APO, FPO and DPO cost different amounts to ship to?
No. USPS treats all three as domestic mail at domestic rates.