I've just experienced a couple of days of incredibly slow browsing (using Chrome mostly, but changing browser didn't help) on my home wi-fi. After trying many things like rebooting the router, removing devices from the network, diagnosing with iStumbler, requesting new DHCP leases, setting manual IPs, I eventually rebooted the machine and everything is back to normal.
What could cause this behaviour?
It's a mid 2014 Macbook Pro with Retina. The wi-fi is an ageing Dynalink that only supports 802.11b/g. I have a VPN installed but not active, and many apps:
It had probably been a few weeks or even a month since the last reboot.
Throughout all these problems, a Macbook Air on the same network worked just fine – so it's not a question of some weird network saturation.
Best Answer
That menu bar looks like you're on Mavericks. You should upgrade to Yosemite and see if that helps.
Speaking of which, if you haven't already, you should check how Internet-using apps that aren't web browsers perform, such as seeing how long it takes Dropbox to download a new file.
If all else fails, you should go to a place with a newer router and see if anything improves.