In this modern era of Apple/Google Pay many folks rarely carry cash–or a wallet. I have met multiple drivers with nothing but their phone in their pocket. And tucked into the case of their phone is a single card: Their driver’s license. Whether pulled over by police or carded at a bar, having your license on you is still required. In fact, police in most states could theoretically ticket you just for forgetting your license at home. But 15 states now allow you to keep your driver’s license or other state-issued ID in an app on your phone. The programs is usually called a mobile driver’s license (mDL).

How does an mDL even work? Well every driver’s license has a unique license ID number. When a police officer has that number, and the name of the state that issued your license, they can almost always look you up to make certain you’re license is current and you’re safe to drive. Many of the ID apps below simply display the license number and sometimes a bar code that certain readers can use to fast-track the process.

There’s a huge range of mDL apps allowed by various states. Some states, such as Louisiana and New York, have developed their own apps as a secure way to keep your driver’s license on your phone. Other states, such as Arizona, trust the secure apps phone manufacturers create to store your credit card info: Apple Wallet, Google Wallet, and Samsung Wallet. Other states, such as Iowa, offer a mix of options. Here’s the full breakdown.

The 15 states with a mDL option to keep your drive’s license on your phone

The Transportation Security Administration maintains a list of states participating in some kind of digital ID program. In addition to these states, the federal government allows you to keep your Passport info on the Google Wallet app to present during domestic flights. But if you’re traveling internationally, you’ll need to bring your physical Passport or other “REAL ID.”