If your iPhone's Wi-Fi disconnects unexpectedly, you may be encountering one of several different problems. You could simply be receiving a poor signal; if the signal is weak or fluctuating, your Wi-Fi reception will reflect this. Your iPhone's software might also be malfunctioning, or you may have damaged the Wi-Fi receptor by dropping the phone or exposing it to liquid.
Before you conclude that something in your iPhone is corrupt, make sure that the Wi-Fi network itself is functioning. Connect to the Wi-Fi network with another device, such as your computer or someone else's iPhone. If you are using a home network, move your iPhone closer to the router. Remove other objects that might be causing interference, such as a baby monitor or a cordless phone. Check that your router and modem are turned on. If you are using a public network, confirm you have entered the correct password and that you do not need to pay for additional time.
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Sometimes, your iPhone's Wi-Fi receptor may need a quick reset. Tap "Settings" on iPhone's home screen and then tap "Wi-Fi." Slide the toggle button to turn off Wi-Fi. Wait five seconds. Slide the toggle button to turn it on again. If this does not help, reset the iPhone itself by holding down the "Home" and "Sleep/Wake" buttons simultaneously until the Apple logo appears.
Update and Restore
If the iPhone does not have the latest software updates or if you jailbroke your phone, it may not operate at optimal levels, and this may be the source of your Wi-Fi malfunctions. To update, connect the iPhone to your computer and open iTunes. Click the iPhone's name in the left column of the iTunes window and click "Check for Updates" in the center of the screen. Choose to download any available update in the dialog box that appears. If this still does not help, restore the iPhone to factory settings by clicking the "Restore" button just below Check for Updates. This completely erases the iPhone and reinstalls the software, so if the Wi-Fi problem has anything to do with your software, it is resolved.
Hardware damage can also be the source of Wi-Fi interruptions. Dropping the iPhone, exposing it to extreme temperatures or liquid damage can all cause permanent harm to the wires and circuit boards responsible for transmitting Internet signals. This type of problem cannot be fixed at home; instead, you must take the device to an iPhone specialist. However, hardware damage is unlikely if this Wi-Fi issue is the only problem you are encountering, as internal damage is usually widespread.