How eSIMs actually work
An eSIM is not an app, and it is not "software pretending to be a SIM." It is a real SIM — the same secure chip technology that lives inside a plastic SIM card — except the chip is soldered into your phone at the factory. What you download is the profile: the small bundle of carrier data (network keys, an ICCID, operator settings) that a plastic SIM would normally carry.
What happens when you scan the QR code
The QR code you receive after buying an eSIM encodes an activation code — a short string that starts with LPA:1$. It tells your phone two things: the address of a provisioning server (called an SM-DP+ server) and a one-time token identifying your specific profile.
When you scan it, your phone contacts that server over the internet, authenticates with the token, and downloads the carrier profile into its embedded SIM chip. The chip verifies the profile's signatures before installing it. From that point on, your phone behaves exactly as if you had inserted a physical SIM from that carrier.
This is also why an eSIM can typically only be installed once: the token is consumed during download, and the profile is bound to the secure chip in that specific device. If you delete the profile or switch phones, the carrier has to issue a new one.
Why travelers care
Because the profile is delivered over the internet, there is no shipping, no airport kiosk, and no fiddling with a SIM ejector tool at baggage claim. You can buy a data plan at home, install it over Wi-Fi, and switch it on when you land.
Modern phones also support multiple profiles side by side. Your home SIM stays active for calls and texts, while the travel eSIM handles data. In your settings you simply choose which line provides mobile data.
What eSIMs from resellers include
Most travel eSIMs — including the ones sold here — are data-only. They do not come with a phone number for calls or SMS. In practice this matters less than it used to: iMessage, WhatsApp, FaceTime, and most two-factor codes either work over data or reach you on your home SIM, which remains reachable.
Quick compatibility check
Your phone needs two things: eSIM hardware (standard on iPhone XS and newer, Pixel 3 and newer, and most recent Samsung flagships) and a carrier-unlocked status. The fastest check: look in your settings for an "Add eSIM" or "Download a SIM" option. If it is there, you are ready.
That is the whole system — a secure chip, a provisioning server, and a QR code connecting the two. The rest is just choosing how many gigabytes you need.