See this screenshot: I'm using a 2012 MacBook Air (max connection rate of 300Mbps) and an ASUS RT-AC68 router. As you can see above, the signal is very strong, there are no problems with noise, yet the transmission rate is just 7Mbps, and at this rate, nothing works. Can't even load the router's web UI, or get reasonable local ping times to it. Something similar actually happens on my iPhone 6 Plus. I narrowed it down to three things: 1) Monday's 10.11.4 / iOS 9.3 updates 2) Router problem 3) Hardware problems The router has been acting normal for a long time. Adjusting the wireless channels and rebooting it didn't seem to do anything. I'd say that my MacBook Air's Wi-Fi/BT card is just having problems, but my 6+ has started doing it as well... And none of this happened until very recently, coinciding with the release of 10.11.4 and iOS 9.3. No idea what to try at the moment.