User level: Level 1 (0 points)Model iMac 27″ 5K Version macOS 13.7.8 has suddenly got slow WiFi. All other Apple devices in the house are flawlessly using 125Mbs. My iMac has dropped to 27Mbs !
[Re-Titled by Moderator]
Original Title: Slow WiFi on iMac
Posted on Oct 9, 2026 1:41 AM
User level: Level 10 (123,805 points)Oct 9, 2026 7:26 AM in response to geofffromhalifax
Your 27-inch 5K iMac running macOS Ventura 13.7.8 has suddenly dropped to 27 Mbps over Wi-Fi, while your other Apple devices achieve approximately 125 Mbps.
This suggests a difference in the iMac's connection or network performance, but the cause is not yet known.
Restart the iMac and repeat the speed test using the same service and location.
Pause any active downloads or cloud synchronization.
If the speed remains low, test closer to the router and compare the iMac's Wi-Fi band with that of a working device.
Hold Option (⌥) while clicking the Wi-Fi menu to check the channel, RSSI, noise level and Tx Rate.
These details may help assess the connection. Then run Apple's Wireless Diagnostics.
If the problem persists, consider whether it began after a macOS update, router change or software installation.
Temporarily disconnect any Commercial VPN, where appropriate, and test the iMac on another Wi-Fi network if available.
These checks can help narrow down the cause before changing network settings.
For further guidance, see Apple's Wi-Fi troubleshooting recommendations.
User level: Level 10 (85,896 points)Oct 10, 2026 9:05 AM in response to geofffromhalifax
Does clicking the WiFI icon in the menubar show more than one router channel option?
Our router/modem has two channels and one is far slower than the other. We've occasionally had a device disconnect and reconnect to the slower channel.
User level: Level 7 (27,833 points)Oct 9, 2026 7:31 AM in response to geofffromhalifax
Start by rebooting your iMac and see if that solves the problem.
Also, have there been any changes recently? For example, have you done any macOS Updates or installed any new apps, has the iMac or router been moved to a different location, are there any devices newly connected to the iMac, etc.
125 Mbps on your other devices is not even that fast. What WiFi router are you using, and are you using 2.4GHz WiFi or 5 GHz WiFi?
Originally posted at discussions.apple.com/thread/256372980