I recently got a new phone, and its internet connection over Wi‑Fi is extremely slow. My old phone still works normally on the same network, and my sister is having the same issue with a phone she bought a month or two ago. Turning off Wi‑Fi on the older devices didn't help. On the new phones, YouTube barely plays and downloads are painfully slow, while mobile data works at full speed. What could be causing Wi‑Fi to be slow only on the newer devices?
3 Answers
Try connecting the new phones to the 5 GHz Wi‑Fi network instead of 2.4 GHz. If that doesn’t help, forget the saved network and connect again. You can also reset the phone’s network settings, although that will remove saved Wi‑Fi passwords and Bluetooth pairings.
Start with a speed test on both an old and a new device while they’re in the same spot. That will show whether the new phones are actually receiving less bandwidth or whether the problem is specific to certain apps. A router running in compatibility mode might reduce performance somewhat, but it normally shouldn’t make basic video streaming unusable.
Your router may be combining its 2.4 GHz and 5 GHz bands under one network name, and the phones might be choosing the slower 2.4 GHz band. In the router’s wireless settings, disable band steering or give the two bands separate names, such as HomeWiFi and HomeWiFi-5G, then connect the phones specifically to the 5 GHz one.
Log in to the router’s administration page or app, open the Wi‑Fi or wireless settings, and look for separate names or SSIDs for the 2.4 GHz and 5 GHz networks. Give them different names, save the changes, and choose the 5 GHz name on the phones. The exact menu depends on the router model.

How do I separate the two bands? I’ve never changed that setting before.