MacBook Slow on 5GHz WiFi? Change Your Router's Channel.

My MacBook Pro M3 was crawling on WiFi. I'm talking 40 Mbps on a 5GHz connection that every other device in the house was pulling 800+ Mbps on. Packet loss was constant. 5GHz was completely unusable—I was getting better speeds on 2.4GHz, which should never happen.

What I Tried First

I run separate SSIDs for 2.4GHz and 5GHz, so I knew exactly which band I was on. I tried everything—disabling WiFi 6, forgetting the network, renewing DHCP, resetting the WiFi module, toggling Bluetooth, different locations in the house. Nothing stuck.

The Breakthrough

I happened to have a spare Eero mesh router. I plugged it in as a quick test—the MacBook connected on 5GHz and instantly hit 800 Mbps. Perfect latency, perfect pings, no packet loss. So it wasn't the MacBook.

I compared the two routers and found the difference:

I swapped back to the ASUS, changed the 5GHz control channel from 149 to 40, and ran a speed test.

How to Fix It

1. Log into your router's admin panel
2. Find the 5GHz wireless settings
3. Change the control channel to 36, 40, 44, or 48 (any UNII-1 channel)
4. Save and reconnect

If your router is set to “Auto” channel selection and it keeps picking a UNII-3 channel, hardcode it to a UNII-1 channel instead. Auto selection doesn't account for client-side compatibility issues.