Methodology
Aggregation and normalisation of public postal and geographic data, with every value traceable to its source.
Principle
CodePostalPro aggregates publicly available postal and geographic information (postal operators, open datasets, collaborative databases), normalises it into a common model — country › administrative region › delegation or post office › locality — and publishes it with its source and a verification status. We never create postal codes: when a value cannot be established, the page says so explicitly.
Normalisation
- Names: sources are often in unaccented capitals. We restore accents for a controlled vocabulary of common French nouns (Cité, Résidence, École, Aéroport…) and keep the original spelling on the page when it differs.
- URL identifiers: lower-case, no diacritics, words separated by hyphens, apostrophes removed. Historical French URLs (2015–2023) redirect one-to-one to their French page under
/fr/. - Hierarchy: every country follows region › group › locality, named in its own terms — United States: state › city › ZIP code; France: région › département › commune; Morocco: région › province › locality; Tunisia — governorate › delegation › locality; Algeria — wilaya › post office › locality (one post office corresponds to one postal code and serves one or more localities).
- Coordinates: taken from the source with its precision level (postal-area centroid, locality…). They power the “nearby localities” lists.
Verification statuses
- Concordant sources — the same value appears in at least two independent sources.
- Single source — value from one source, not cross-checked.
- Conflicting sources — sources give different values; the page shows all of them with their origin.
- Unverified — no usable source; the page only carries geographic information.
Pages without sufficient information are excluded from search engines (noindex) until improved.
United States
ZIP codes, city names, counties and coordinates come from GeoNames (CC BY 4.0), which compiles USPS data. A ZIP code is a delivery route, not a boundary: it can span cities or counties, and the city shown is the primary USPS name. Military (APO/FPO) ZIPs are excluded. Three enrichments are added, each labelled on the page: demographics (population, median household income, median age) from the Census Bureau’s ACS 5-year estimates for the ZCTA — the Census approximation of the ZIP area — covering about 82 % of ZIPs; telephone area codes from NANPA’s central-office assignment records, matched by rate centre to the city (cities without a rate centre of their own take the nearest matched city within 40 km and say so); and the time zone of the nearest populated place.
France
Communes and postal codes come from GeoNames (CC BY 4.0), built from La Poste’s open data. One postal code usually serves several communes, so a code page lists every commune it covers. CEDEX codes (business and bulk delivery) are excluded as non-geographic. Région and département names follow the 2016 territorial reform; historical URLs using the former region names redirect to the current ones.
Germany
Localities, Kreise and postal codes come from GeoNames (CC BY 4.0). Each Land is grouped into Kreise (districts and independent cities) built from GeoNames’ third administrative-division field, which is the level that reliably corresponds to a Kreis across all 16 Länder. This is a single-source, not cross-checked dataset: Deutsche Post’s own postal file is commercially licensed and could not be used. Some entries reflect dedicated postal codes issued to large mail recipients (“Großkunden-PLZ”) rather than towns; these are a normal, deliverable part of the German postal system.
Austria
Localities, Bezirke and postal codes come from GeoNames (CC BY 4.0). Each Bundesland is grouped into Bezirke (political districts and statutory cities), built from GeoNames’ second administrative-division field, which reliably corresponds to the Bezirk level across all 9 Bundesländer. This is a single-source, not cross-checked dataset, pending an official cross-check (e.g. Statistik Austria).
Spain
Localities, provincias and postal codes come from GeoNames (CC BY 4.0). Each Comunidad Autónoma is grouped into Provincias (provinces), built from GeoNames’ second administrative-division field, which is 100 % filled and reliably corresponds to the province level across all 19 Comunidades Autónomas (including the autonomous cities of Ceuta and Melilla). This is a single-source, not cross-checked dataset, pending an official cross-check (e.g. Correos). English pages only for now; a Spanish-language edition is planned for a later phase.
Morocco
Provinces, localities and postal codes come from GeoNames (CC BY 4.0). Regions follow the 2015 administrative division (12 régions); historical URLs using the former 16 regions redirect to the current ones.
Tunisia
Hierarchy and codes follow La Poste Tunisienne’s lookup service (governorate › delegation › locality), via a structured community transcription, cross-checked with a second dataset (Arabic names, coordinates and main code of each delegation). The 17 delegations and localities of Tunis, Bizerte and Jendouba still referenced by Wikipedia were checked individually: the main code of each delegation agrees in both datasets. Direct verification on poste.tn, unreachable from our environment at build time, will be repeated.
Algeria
Place names, wilayas, post-office groupings and coordinates come from GeoNames (CC BY 4.0). Caution: Algeria renumbered its postal codes in 2008; the numbering found in GeoNames differs, for a large share of post offices, from the post-2008 list compiled from Algérie Poste (e.g. Hydra: 16016 in GeoNames, 16035 in the 2008 list). We could not consult Algérie Poste’s website directly (connection refused, no archive available). Consequently:
- the GeoNames value is shown as the primary value, with its source;
- when Wikidata or the Wikipedia list give another value for the same locality, it is shown alongside (“Other recorded value”) and the page gets the “Conflicting sources” status;
- a value is only called “concordant” when two independent sources give it.
Algérie Poste’s official list will be integrated as the reference source as soon as it can be consulted; affected pages will be updated and the history of values kept.
Limits
- Postal codes and administrative boundaries change; a page reflects the generation date shown at its bottom.
- Sources may contain typing errors, duplicates or obsolete names.
- Postal operators (USPS, La Poste, Poste Maroc, La Poste Tunisienne, Algérie Poste) remain the sole authority.
Corrections
Every page has a “Report an error” link. Give the page address, the expected value and, if possible, a verifiable source (postal operator’s website, official document). Open the form.