France has a public API for every land parcel in the country — and almost nobody knows it

If you own, rent, or are thinking of buying property in France, there is a
piece of information you probably need at some point: the cadastral reference of a land parcel — a unique identifier that tells you exactly which plot of land you are dealing with, its official surface area, and which administrative entity it belongs to.

The good news: France makes all of this data available for free, through a public API maintained by the government. No registration. No API key. No rate limit for reasonable usage.

The bad news: almost nobody outside the GIS and real estate professional
world knows it exists.

What is the "Cadastre"?

The French cadastre (cadastre in French) is the official land register.
It was created under Napoleon in the early 19th century and has been
continuously maintained and digitized ever since.

Every plot of land in France — from a Parisian studio apartment building to a vineyard in Burgundy — has a unique cadastral reference in the format:

[Department code] [Section] [Parcel number]
e.g.:  75   AX   0142
       ↑    ↑    ↑
  Paris  section  parcel

This reference is used in notarial deeds, building permits, property
tax declarations, land surveys and virtually every official document
related to real estate in France.

The API: apicarto.ign.fr

The IGN (Institut National de l'Information Géographique et Forestière)
is the French government agency responsible for geographic data. They
maintain a free, open REST API called API Carto that exposes the
Plan Cadastral Informatisé (PCI) — the digital cadastral map of France.

You can query it by:

• Coordinates (longitude, latitude) → get the parcel under that point
• Commune + section + number → get the parcel geometry
• INSEE code → list all parcels in a commune

The API returns standard GeoJSON, so it works with any mapping library
or GIS tool out of the box.

The problem with the official tools

While the data is public and the API is open, using it is not exactly
user-friendly for the average person:

• The official government viewer (cadastre.gouv.fr) requires knowing the commune name and navigating a dated interface.
• The Géoportail is powerful but complex.
• The raw API is for developers, not for the general public.

There is a clear gap between "the data exists and is free" and
"anyone can access it easily".

Bridging the Gap

That is the exact problem we set out to solve with
RefCadastrale.fr.

The idea is simple: take the open government data and present it in a
clean, fast, searchable interface that works for everyone — whether you
are a notary verifying a deed, a citizen curious about their neighbor's
plot, or a developer looking up parcel references for a project.

On RefCadastrale.fr you can:

• Search any address in France and instantly see the cadastral reference
• Browse parcels by department, commune and street
• See the official surface area (contenance) in m²
• Get the INSEE code and section information
• Access direct links to official government sources

A Practical Example

Say you want to know the cadastral reference of the land under the
Eiffel Tower. Here is what the IGN API returns for those coordinates:

{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "properties": {
      "commune": "75056",
      "section": "EO",
      "numero": "0001",
      "contenance": 24116,
      "feuille": 1
    }
  }]
}

Surface: 24,116 m² (about 2.4 hectares). That is the official
registered size of the Champ de Mars parcel in the 7th arrondissement.

Who Uses This Kind of Data?

Cadastral data is more useful than most people realize:

• Home buyers and sellers — verifying that the surface area in the contract matches the official cadastral record
• Architects and urban planners — understanding plot boundaries before designing a project
• Lawyers and notaries — cross-referencing deeds with official records
• Journalists — investigating land ownership and urban development
• Developers and data scientists — building location-based apps with reliable French geographic data
• Curious citizens — understanding who owns what in their neighborhood

Open Data, Open Possibilities

What makes this particularly exciting from a developer's perspective is
that France's open data ecosystem has become genuinely excellent in
recent years. Between data.gouv.fr, api.gouv.fr, and the IGN's API Carto, you have access to:

• Full cadastral map of France (PCI)
• Address database (Base Adresse Nationale)
• Administrative boundaries (communes, departments, regions)
• Topographic data
• Historical aerial photography going back decades

All free, all open, all with permissive licenses.

Try It Yourself

If you want to explore French cadastral data without writing a single
line of code, RefCadastrale.fr is the fastest way to get started.

If you are a developer and want to query the API directly:

GET https://apicarto.ign.fr/api/cadastre/parcelle
    ?geom={"type":"Point","coordinates":[2.2945,48.8584]}
    &_limit=1

No API key required. No registration. Just a GET request.

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France digitized its entire land registry and made it freely available.
That is genuinely remarkable. The only shame is that so few people know it exists.

Have you used the French cadastral API in a project? Share it in the comments — I would love to see what people are building with it.