Glossary of Mexican address terms

Código postal (CP)

A código postal is the five-digit number SEPOMEX assigns to a delivery area in Mexico. It identifies an area rather than a building: one code usually covers several named asentamientos, and it is written before the municipio and the estado, never after them.

There is nothing equivalent to ZIP+4. Five digits is the whole code, leading zero included — 06700 is a real code in Ciudad de México and 6700 is not one, which is why storing a CP as an integer breaks first and worst in the capital.

Asentamiento

An asentamiento is the postal catalog’s unit for a named populated area inside a postal code — the line on the form nearly everyone calls the colonia. Each one carries a tipo de asentamiento saying what kind of place it actually is.

The catalog holds 159,019 of them, sorted into 24 kinds.

It is the term to use when you mean the entry rather than the neighbourhood, and the reason an address field labelled “colonia” will happily be filled in with a rancho, an ejido or an airport.

Colonia

A colonia is one kind of asentamiento: a named neighbourhood, normally urban. It is what Mexicans call the field on every address form, whatever the catalog happens to call the entry that goes in it.

It is not even the most common kind. Of the 159,019 asentamientos in the catalog, 47,139 are filed as Colonia — the largest single type is Ranchería, with 50,347.

So labelling the field “colonia” is fine — that is the word people know. Assuming the value is one is not.

Tipo de asentamiento

The tipo de asentamiento is SEPOMEX’s classification of a populated area: Colonia, Fraccionamiento, Barrio, Pueblo, Ranchería and a couple of dozen others. The API returns it next to the name, as settlement_type.

The values are Spanish and capitalized exactly as the catalog writes them, on both languages of this site, because that is the literal string that comes back in the response. The full list, with how much of the catalog each one accounts for, is below.

Municipio

A municipio is the second level of Mexican government, sitting under the estado — roughly what a county is elsewhere. Every address in the country is inside exactly one, and it is a level of government rather than a size of place: a municipio can be a city or a stretch of countryside.

There are 2,478 of them across the 32 estados.

INEGI gives each one a three-digit clave that is unique only inside its estado, so the pair is the identifier — not the name, which is shared more often than anyone expects.

Alcaldía

An alcaldía is what Ciudad de México calls its municipios. They are the only ones in the country with that name, and they replaced the older delegaciones in 2016.

There are 16 of them, and SEPOMEX files them in the same municipios table as everywhere else — so nothing about the request changes, and the API returns them under municipality like any other.

Ciudad

Ciudad is an optional field in the postal catalog naming the urban area a code belongs to. It is not a level of government, it does not nest tidily inside a municipio, and it is frequently blank.

20,407 of the 31,880 postal codes in the catalog carry no ciudad at all. Treat it as a label you can display, never as a key you can join on.

Localidad

A localidad is INEGI’s unit for a populated place — a town, a village, a hamlet — defined for censuses and statistics rather than for post. It is the word people reach for when they mean “the place”, and it is not another word for colonia.

The postal catalog does not carry it. A postal-code lookup answers with the estado, the municipio, the ciudad where there is one, and the asentamientos inside the code — there is no localidad in the response above, because there is none in the source. If a form you are handed asks for one, it is asking an INEGI question, not a postal one.

Estado (entidad federativa)

An estado is one of the 32 entidades federativas that make up Mexico, Ciudad de México included. Each has a two-digit INEGI code, and everything else in the catalog hangs underneath it.

Names drift here too: the catalog says Michoacán de Ocampo and Veracruz de Ignacio de la Llave where a form would say Michoacán and Veracruz. The two-digit code does not drift.

Zona (urbano, rural, semiurbano)

Zona is a field on every asentamiento saying whether it is urbano, rural or semiurbano. It is SEPOMEX’s own classification, and it is the fastest way to tell a city neighbourhood from a hamlet that happens to share its name.

More of the catalog is rural than urban — 93,594 asentamientos against 64,922 — which is the opposite of what the word colonia suggests, and worth knowing before you size a dropdown.

SEPOMEX

SEPOMEX is the Servicio Postal Mexicano, Mexico’s national postal service. It assigns the postal codes and publishes the Catálogo Nacional de Códigos Postales, which is the source underneath every postal-code product in the country, this one included.

It is an abbreviation of the institution, not of the catalog, so “the SEPOMEX file” and “the SEPOMEX API” are both shorthand rather than product names.

Clave INEGI

A clave INEGI is the numeric code the national statistics institute assigns to a place: two digits for the estado, three for the municipio inside it. Jalisco is 14, Guadalajara is 039, and 14039 is that municipio and no other.

This is the identifier to match on whenever records cross a system boundary — invoicing, government filings, logistics partners and public datasets all speak it. Names do not survive that trip.