On macOS, someone below recommended "WiFi Signal", USD 5.
Not so fully featured, I assume, but free is Wireless Diagnostics. Ignore the popup, and go to Windows -> Info/Scan/Performance
(it's in System -> Library -> CoreServices -> Applications, but I start it via Spotlight)
> Not so fully featured, I assume, but free is Wireless Diagnostics. Ignore the popup, and go to Windows -> Info/Scan/Performance (it's in System -> Library -> CoreServices -> Applications, but I start it via Spotlight)
Protip: it's also easily accessible by holding Option and clicking on the Wifi icon in the menu bar.