How an address is written in Belgium

The order the lines go in

The parts are named rather than filled in: Spaw does not know an address in Belgium and will not invent one. This block is produced by the same function that rewrites a real address, so the line order, the capitals Belgium asks for and any text its operator prints on every envelope are the checker's own behaviour rather than a second description of it.

Organisation
Street name 12
Flat or unit
Postal code Town or city

No recipient line: nothing in the response is about a person, so the name the envelope carries is not part of what is checked.

In Belgium the house number follows the street name, and that is the side it is written back on when the checker rewrites an address. The postal code is written before the town.

Can Spaw tell whether an address in Belgium exists?

Yes. Belgium's BeST Address register (FPS BOSA) lists 4,921,654 addresses in Flanders, Wallonia and Brussels (oldest file 31 October 2026). Each regional file is declared a complete address register for its region and together they are the whole country, so an address one of them holds answers exists: true and one none of them holds answers exists: false. A false has two honest failure cases: a building added after the version in use, and an address spelled so differently from the register that no variant of its street matches. That is why a miss is scored rather than refused.

A postcode directory answers a different question. The postal code is settled separately by GeoNames' postal code list, which is recorded as complete: one it does not hold answers postcode_not_found.

Further reading: How to read an address-existence answer and How an open register locates a building.

Check an address in Belgium

The same lookup the API runs, with Belgium already selected.

The postal code

Postal codes in Belgium are four digits.

pattern \d{4}

What Belgium calls an address that is not a front door

A PO box, a private mailbox and the other kinds of delivery point below are told apart by the words written on the address, never by a list of whose box is whose. The rows marked as the operator's own words are taken from the addressing guide of the postal operator in Belgium; the others are international spellings, not the operator's own. All of them are what the checker reads, and because an entry is carried for Belgium, an address here with none of them answers street.

The anchored spellings are the conservative half of this: those words are ordinary language elsewhere in an address, so they only count when they open the line and carry a number after them.

BUS, BTE, BOITE, BOX look like box words in Belgium but name a flat or suite. They classify nothing; they only tell the parser where the unit is.

What can be checked for an address in Belgium

Read from the datasets this server holds right now, not written into the page. For most countries the answer is the written form and the postcode shape and nothing beyond them — in particular not the row people assume is always there.

Null means not evaluated, never no.

Other countries

• Australia
• Åland Islands
• Azerbaijan
• Barbados
• Bahrain
• St. Barthélemy
• Brazil
• Canada
• Check any address
• Every dataset behind the checker

Sources

• Google's Address Data Service · address-formats 2026-09-05© Google LLC, CC BY 4.0 (Google Address Data Service); initial import via commerceguys/addressing (MIT)
• The postal operators' addressing guides · address-rules 2026-09-17
• Belgium's BeST Address register (FPS BOSA) · be-best-address-flanders 2026-10-31BeST Address — Flanders (Digitaal Vlaanderen via FPS BOSA), CC BY 4.0
• Belgium's BeST Address register (FPS BOSA) · be-best-address-wallonia 2026-10-31BeST Address — Wallonia (Service public de Wallonie via FPS BOSA), CC BY 4.0
• Belgium's BeST Address register (FPS BOSA) · be-best-address-brussels 2026-10-31BeST Address — Brussels (CIRB/paradigm.brussels via FPS BOSA), CC BY 4.0
• GeoNames' postal code list · geonames-postal-codes 2026-10-31Postal codes, places and centroids from GeoNames (geonames.org), CC BY 4.0.

Data synced on 2026-10-31: the newest version among the datasets listed above.