France Postcode Validator

French postcodes — called code postal — follow a compact, well-defined five-digit format established by La Poste and codified by INSEE (Institut National de la Statistique et des Etudes Economiques). Unlike many country postal systems, every French postcode is purely numeric and exactly five digits long. The first two digits map directly to the administrative department, which means that knowing a postcode tells you immediately which of France’s 96 metropolitan departments (or 5 overseas departments) a location sits in — without any extra lookup.

This validator checks any code postal against the complete La Poste / INSEE department registry. It confirms the correct length, verifies the department prefix is recognised, identifies the department by name, the administrative region that contains it, and the territory classification (metropolitan France, overseas department, or special collectivity). For Paris, Lyon, and Marseille — the three French cities that subdivide their postcodes further — it also extracts and labels the specific arrondissement.

How it works

Step 1 — Normalise. Whitespace is stripped. Only digits are accepted; any letter or symbol triggers an immediate, plain-language error message pointing to the offending position.

Step 2 — Length check. French postcodes must be exactly five digits. The validator rejects anything shorter or longer, explaining how many characters were found.

Step 3 — Department lookup. The first two or three digits are matched against the department table. For metropolitan France, prefixes 01 through 95 are used (with 20 covering the Corsican postcodes, since the island uses 20xxx codes even though its administrative departments are coded 2A and 2B). For overseas departments, the three-digit prefixes 971 through 976 are tried first. For special collectivities (Monaco, French Polynesia, New Caledonia, Wallis-et-Futuna, Saint-Pierre-et-Miquelon), three-digit series in the 975 and 980–989 range are recognised. Any unrecognised prefix (such as 96xxx or 99xxx, which are unassigned) is flagged with a clear explanation.

Step 4 — Arrondissement annotation. For Paris (75001–75020), Lyon (69001–69009), and Marseille (13001–13016), the last digits are parsed to identify the arrondissement and an extra note is displayed beneath the main result.

Step 5 — Output. The validated postcode, department name, region, and territory type are shown in a structured table alongside a copy button.

Worked example

Suppose you want to check the postcode 75008 — the 8th arrondissement of Paris (home to the Champs-Elysees and the Arc de Triomphe):

• Length: 5 digits — correct
• First two digits: 75 — department “Paris”, region “Ile-de-France”, type metropolitan
• Suffix 08: Paris 8e arrondissement
• Result: Valid — Paris, Ile-de-France (8e arrondissement)

Now try 69002 (the 2nd arrondissement of Lyon, Presqu’ile district):

• First two digits: 69 — department “Rhone”, region “Auvergne-Rhone-Alpes”
• Suffix 02: Lyon 2e arrondissement
• Result: Valid — Lyon, Auvergne-Rhone-Alpes (2e arrondissement)

And try 97100 (Basse-Terre, Guadeloupe):

• First three digits: 971 — overseas department “Guadeloupe”, DOM
• Result: Valid — Guadeloupe, Overseas Departments (DOM)

Everything runs locally in your browser — no postcode you type is ever sent to a server.