APN stands for Access Point Name. It's a configuration setting that tells your phone how to reach your carrier's data network. Without the right APN your phone can connect to a tower for calls and SMS but won't get internet.
Where you'll see it
Settings → Mobile/Cellular → APN. Most carriers ship SIMs that auto-configure the APN — you'll never see it. But if you swap SIMs or import a phone, you may need to enter the APN manually.
Fuse APN
Fuse eSIMs configure the APN automatically when you scan the activation QR code. You shouldn't need to touch this setting.
When manual setup is needed
- Imported phone from another country
- Older devices without auto-config
- Some carrier-locked devices when switching providers