[Digital Today reporter Yoonseo Lee] A smartphone that keeps moving from Wi-Fi to mobile data is generally a sign that there is a problem with the Wi-Fi connection.

According to the IT outlet Engadget on Nov. 10, smartphones check signal strength, speed, latency and packet delivery in real time to maintain calls, streaming and messaging connections, then automatically switch to the more stable option.

Most switches happen without the user noticing, but the changeover can drop FaceTime calls or interrupt some tasks that require a Wi-Fi connection.

The most common cause is a weakened Wi-Fi signal. Typical cases include moving farther from the router or having obstacles such as walls or furniture interfere with the signal.

Each frequency band has different characteristics. The 2.4 GHz band has a wider range and is better at passing through obstacles. The 5 GHz band offers faster speeds but has a shorter range, while the 6 GHz band can deliver high speeds but has an even shorter range and is more affected by obstacles.

Carrier disruptions are not the only cause. Network congestion or router malfunctions can also trigger the switch. If a smartphone shows a message saying there is no internet connection, it is necessary to check whether the router or external internet line has a problem rather than the Wi-Fi signal.

Operating system settings are also a factor. On iPhones, iOS 27 uses a feature called Connection Assist to use Wi-Fi and mobile data together to keep connections stable. In iOS 26 and earlier, Wi-Fi Assist provides the same function. Samsung Galaxy and Google Pixel phones also offer options to automatically switch to mobile data. If only a particular phone keeps switching to mobile data, the automatic switching feature is likely turned on.

It is also possible to disable automatic switching. On iPhones, users can go to Settings > Wi-Fi or Cellular and turn off the relevant feature. On Samsung Galaxy phones, it can be disabled under Intelligent Wi-Fi in the Settings > Connections > Wi-Fi menu. On Google Pixel phones, users can turn off automatic switching in Wi-Fi preferences under the Network & internet menu.

This approach can further worsen connection quality. Checking the cause should take priority over changing settings.

A fundamental solution is to remove the cause of switching. Options include widening coverage with a Wi-Fi extender or mesh system, or turning the router off for at least 30 seconds and then turning it back on. Users should also check for outages at their internet service provider (ISP) and confirm router firmware updates.

If mobile data usage is a concern, another option is to set Wi-Fi-only tasks by app. Restricting downloads, cloud backups and syncing to run only on a Wi-Fi connection can reduce data consumption.

Ultimately, switching between Wi-Fi and mobile data is closer to a basic function to maintain connectivity than a malfunction. If switching repeats only in a specific room, check for a weak signal. If a warning appears that there is no internet while connected to Wi-Fi, check the router or internet line. If other devices are fine but only a user's phone switches, the automatic switching setting should be checked first.