With the iPhone 14, Apple has worked up the courage to remove yet another physical connector.

This time it’s the slot for the physical SIM card that cellular networks use to identify their subscribers. In the United States, Apple will only sell the iPhone 14 without a SIM card slot, and will instead only support eSIM, which embeds a digital version of the card inside the phone itself.

Much like the headphone jack before it, Apple is pitching its move to ditch physical SIM cards as a boon for consumers. The company says eSIM is more secure and easier to connect, and it allows customers to add multiple lines on a single phone, each with their own phone numbers.

But the move to kill off physical SIM cards will also cause a lot of problems in the short term, most notably by limiting customers’ choice of carriers both at home and abroad.

Here’s everything you need to know–both good and bad–about Apple’s switch to eSIM.

HOW DO YOU SET UP AN ESIM?

Apple currently offers three ways to set up an eSIM:

• eSIM Quick Transfer wirelessly converts a physical SIM on one phone to an eSIM on another, or moves an existing eSIM between phones.
• eSIM Carrier Activation turns on a new line of service as part of the iPhone’s initial setup process.
• Carrier apps or websites serve as a fallback for carriers that don’t support the above methods. After users provide their account credentials, they can scan a QR code to set up an eSIM on the new phone.

In the United States, all three major carriers–AT&T, T-Mobile, and Verizon–support Quick Transfer and Carrier Activation, so the setup should be fairly simple. Some smaller “MVNO” providers and overseas carriers support these activation methods as well, according to Apple’s website.

For carriers that don’t support Apple’s Quick Transfer and Carrier Activation tools, setting up an eSIM may be more of a hassle than swapping a physical SIM card, but it beats having to go out and buy a new card if you don’t already have one.

Due to the finicky nature of physical SIM cards, eSIM may also be easier for some folks either way. “Those SIM card trays and holes are a nightmare for people with fine motor control difficulties,” says Techsponential analyst Avi Greengart.

WHAT ARE ESIM’S ADVANTAGES?

For users, eSIM offers a few of clear advantages over physical SIM cards:

• It’s more secure, because no one can remove it from the phone and use it to intercept phone calls or text messages. (This isn’t the most common form of SIM card hijacking, but it is still possible for someone with physical access to the phone.)
• Switching carriers is easier, because you don’t have to wait for a SIM card to arrive or pick one up at a store.
• Adding extra lines is easier, because you no longer need a phone with dual SIM card trays. (On the iPhone, Apple supports up to two phone numbers and eight data lines with eSIM.)

An eSIM benefits phone makers and wireless carriers as well. For Apple, eliminating the SIM tray means freeing up more precious space inside the device, which it can use to pack in additional technology. And as Greengart points out, they’re a money-saver for carriers, who no longer have to spend what he estimates is $10 to $20 per physical card.

IS ESIM COMPATIBLE WITH EVERY U.S. CARRIER?

Unfortunately, no. Some alternative providers that lease capacity from the major carriers–known as Mobile Virtual Network Operators, or MVNOs, in industry jargon–don’t support eSIM today, which means you can’t use an iPhone 14 on their networks.

Jeff Fieldhack, a research director for CounterPoint Research, estimates that roughly 60% of MVNOs don’t yet support eSIM, but those that do offer eSIM support cover roughly 85% of total subscribers. Some notable exceptions include Ting, Walmart Mobile, US Mobile, Net10, and Tello.

Whether that will change in the near future is unclear. Ting, an MVNO owned by Dish Network, has previously bemoaned the difficulties of adopting eSIM, and has not yet committed to adding it for the iPhone 14.

“This transition is definitely going to be hardest for MVNOs who need to update their infrastructure and processes and hope that they don’t lose too many subscribers in the process,” Greengart says.

IS ESIM A PROBLEM FOR OVERSEAS TRAVEL?

Right now, yes. Some countries’ wireless carriers still require a physical SIM card, and for countries that do allow for eSIM, the options are sometimes limited. Over at XDA-Developers, Adam Conway points to Ireland as an example, noting that you can only get an eSIM through Vodafone, whose pay-as-you-go plans are twice the price of other local carriers.

If you can’t activate an eSIM from a local carrier, you can look to worldwide service providers such as Airalo and Ubigi, but these tend to be pricier than local options, and they only cover data, so you can’t get a local number to contact businesses in the area.

HOW WILL ESIM AFFECT COMPETITION BETWEEN CARRIERS?

In theory, eSIM could make the wireless business more competitive by lowering the barriers to switching. A company like Apple could even potentially offer a marketplace of some kind, in which users could easily shop around for service from different carriers.

That said, wireless carriers have other ways of locking you in, such as the generous subsidies they offer on new iPhones in exchange for long-term payment plans. You can’t switch carriers without losing those subsidies, so leaving is hard even if eSIM technically makes it easier.

WILL ESIM MAKE UNLOCKING YOUR PHONE ANY EASIER?

eSIM has no bearing on whether a phone is locked or unlocked. If your phone is locked to a specific carrier, you can’t add another eSIM card to it, for instance while traveling overseas. (Verizon automatically unlocks new phones after 60 days for postpaid customers, even for phones on installment plans, but AT&T and T-Mobile both require you to pay for the phone in full first.)

WHAT DOES ESIM MEAN FOR THE GEEKS WHO CONSTANTLY SWITCH BETWEEN PHONES?

This is one area in which eSIM will likely be more annoying over the long term. Instead of just being able to swap physical SIM cards–a process that takes less than a minute–you’ll have to go through the wireless carrier’s app or online portal to transfer service.

Verizon spokesman George Koroneos notes that you won’t have to pay an activation fee each time, that’s just if you’re activating a new line, but the process could still be a hassle given that you have to get the carrier involved in the first place.

Most users will never have to worry about this, but spare a thought, if you will, for the gadget reviewers, industry analysts, and tech enthusiasts who do.

“I’m expecting this to be a personal nightmare, but we’ll see,” Greengart says.