How many digits is an Italian CAP?

Exactly five. The CAP (Codice di Avviamento Postale) is always a 5-digit number, often written with a leading zero such as 00184 for Rome, so any value that is not five digits is invalid.

What do the leading digits mean?

The first digit identifies a macro-region and the first two digits identify a postal area roughly aligned with provinces and large cities. For example 00 is Rome, 20 is Milan, and 80 is Naples.

Does a valid format mean the address exists?

No. Format validation only confirms the code is a plausible 5-digit CAP and maps it to an area. It does not verify that the CAP serves a specific street or building; use the Poste Italiane lookup for that.

Why do some CAPs start with a zero?

Rome and parts of Lazio and Sardinia use leading zeros (00xxx, 09xxx). Always store and transmit CAPs as 5-character strings so the leading zero is preserved rather than dropped by numeric formatting.

Is my postal code sent anywhere?

No. The format check and area mapping run entirely in your browser, so the CAP never leaves your device.

Italy CAP Postal Code Validator

A CAP (Codice di Avviamento Postale) is Italy’s 5-digit postal code, equivalent to a ZIP code. Validating the format and the geographic prefix catches the most common address-entry errors in e-commerce checkouts and direct-mail lists before they cause failed deliveries.

How it works

Strip non-digits and confirm the code is exactly 5 digits.
The first digit identifies a macro-region (0 = centre/Lazio/Sardinia, 1 = north-west, 2 = Lombardy/west Veneto, and so on up to 9 = Sicily/southern Sardinia).
The first two digits narrow it to a postal area aligned with major provincial capitals — 00 Rome, 10 Turin, 20 Milan, 40 Bologna, 50 Florence, 80 Naples, 90 Palermo, and others.

The tool reports the matched area and macro-region so you can sanity-check that the CAP is consistent with the city on the address.

Example

00184 is five digits and starts with 00, which maps to Roma (Lazio) — consistent with a central-Rome address. A code like 2018 would fail because it has only four digits.

Notes

Format validation and prefix mapping confirm the code is plausible and place it geographically. They do not prove the CAP serves a specific street; for a definitive street-level lookup use the official Poste Italiane service. Everything here runs locally in your browser.