"Biometric" just means measurements of the body, here mainly the shape of your face as captured in your passport photo. Instead of only printing your photo on the page, the passport also stores a digital version of it on the chip, so border systems can compare the document, the data and the person standing in front of them.
Names vary. You'll see e-passport, ePassport, biometric passport and chip passport used loosely. The international standard calls the document an eMRTD (electronic machine readable travel document), and a passport book of that kind an eMRP. The standard is ICAO Doc 9303, which most countries follow, so the basics look similar worldwide. Details such as which extra biometrics are stored vary by issuing country.
What a biometric passport is
The International Civil Aviation Organization (ICAO) sets the rules. Under its standard, a document may only be called an eMRTD, and may only display the chip symbol, if it contains a contactless chip with enough storage for the mandatory data and every entry is secured with a digital signature. The digital signature is the point: it lets a reader check that the data was written by the issuing authority and hasn't been altered.
The standard makes one biometric mandatory, the facial image. Fingerprints and iris images are optional, and each issuing country decides whether to include them. The chip is contactless, so it is read by holding the passport near a reader rather than plugging anything in.
Don't confuse the chip with the printed lines at the bottom of the photo page. That's the machine-readable zone, which is read optically, not electronically.
What it looks like
| Feature | What it is | Where to find it |
|---|---|---|
| Chip symbol | Standard mark showing the passport has a compliant contactless chip | Front cover, near the top or bottom; often also printed on the data page |
| Data page | Photo, name, dates, passport number | Inside the book; the State Department describes its next-generation US book as having a polycarbonate data page |
| Machine-readable zone | Two lines of printed characters, read optically | Bottom of the data page |
| Chip data | Mandatory facial image, plus any optional fingerprint or iris data the country includes | Inside the chip; read electronically |
| Digital signature | Lets readers detect altered chip data | Stored with the chip data |
| Card Access Number (CAN) | Optional 6-digit number letting a reader open the chip without reading the printed lines | On or beside the data page, if the country uses it |
The CAN is an issuing-country choice, so many passports don't show one.
What to keep and for how long
Treat a passport like the high-value document it is. Keep the book itself in a safe place at home, and keep a copy (photo or scan of the data page) somewhere secure but reachable, in case it's lost abroad.
Two dates matter more than most people think. First, the expiry date, since some countries require validity beyond your trip dates; see the passport six-month rule and the passport validity calculator. Second, the date you'll need to start renewing. If you've been wondering how long a passport is valid, that guide covers the usual adult and child periods and how to look up your own.
If something looks wrong with your passport, ask your passport authority before you travel. In the US, USA.gov points you to the State Department for renewing, correcting, or replacing lost or stolen passports.
For a printed or photographed copy, a simple habit works well: file it with your other IDs, and put the expiry in your reminders. The document expiry tracker is built for exactly that.