What does a red battery icon indicate on an iPhone?

A red battery icon on an iPhone is an indication that the battery level is critically low and that the device requires charging soon. This visual cue serves as an alert to the user that the remaining battery power is insufficient for normal operation, prompting them to connect their device to a power source to prevent the phone from shutting down.

In contrast, a charging battery icon would appear as a green or yellow icon, depending on whether the device is fully charged or in the charging process. Airplane mode, indicated by an airplane icon, shows that the device is disconnected from wireless networks but does not impact the battery icon directly. Safe mode does not have a specific battery icon and is typically associated with troubleshooting software issues, not battery status. Thus, the red battery icon is specifically tied to low battery power and the need for charging.