Swapping a SIM while the phone is on is usually fine, Engadget says, but a restart can help

Engadget reported that physical SIM replacement involves opening the SIM tray, usually by gently pushing a paperclip or SIM ejector tool into the pinhole on the phone, changing the card, and reinserting the tray. Users should ensure the replacement card is the correct size and, on dual-SIM phones that accept two physical cards, check which SIM they intend to swap before starting. The phone may then request a PIN or a restart.

The article separates physical SIMs from eSIMs. It said eSIM replacement should be as simple as using a QR code, a carrier app or direct transfer between smartphones. Most eSIM-compatible phones can store several eSIM profiles, though only a few can be active at once. Physical SIMs remain useful for over-the-counter pay-as-you-go accounts and for users who value the relative privacy and convenience of a removable card, Engadget said.

Most risks in a physical SIM swap are physical, according to the report. Dirt, grime or moisture can enter the tray; a larger card can be forced into a smaller slot; or the tray or card can be damaged. A damaged or incorrectly inserted SIM may cause the phone to keep trying and failing to establish a network connection, draining the battery and causing the device to overheat. Engadget said most people never encounter these problems when they slow down and handle the tray carefully. In most cases, the phone takes a moment to read the new SIM and find the network, with service subject to account setup requirements.

Turning the phone off before a swap forces it to read the new card's information when it powers back on, which can help it register on the new network faster and reduce the chance of a software-based network error, the report said. As an alternative, users can enable airplane mode, wait 30 seconds before swapping the SIM, and turn airplane mode off after the new card is inserted. Engadget said this should produce a similar refresh of carrier settings without a full shutdown.

The report also noted that before the 2010s, SIM slots were usually located beneath a phone's removable battery, which required powering off the device to access. As removable batteries became less common, SIM trays moved to the outside of phones. Early models with external trays often showed a network error when a SIM was swapped while the phone was on, but phones quickly became hot-swappable and the problem faded, according to Engadget.

Some Android devices still include a microSD card slot, sometimes in the same tray as the SIM. Engadget warned that users should unmount the microSD card before removing it to prevent data loss. On Samsung devices, the publication said, users can open the My Files app, find the SD Card, tap the three-dot menu next to it and choose Unmount. If a network error appears after a SIM swap, Engadget advised restarting the device first.