Q: Why in OS X Mavericks internet is so slow?

Try using a DNS server outside of your home network

Google's is 8.8.8.8

System Preferences > Network

I am on Mavericks and everything on wifi/network is working perfectly.

Now it's working. What it did for me was configuring my router to use another radio channel. Still, the odd thing is why all the other devices worked well all along except for my MacBook right after upgrading to Mavericks.

I'm having the same problem.  Using Safari or Firefox, when I click on a link, the name is updated in the tab really quickly; however nothing happens for a long time after that. 

I read about someone using ethernet, and decided to plug my Mac Mini into my old Airport Express, and use a faux-wired connection, and sure enough, works like a charm.

My Mac Mini has a much newer wireless card in it, so I'd imagine that overall I'd get faster speeds without the Express, it just seems to be an issue with web browsing as streaming through WAN and pretty much everything else works without a hitch. 

Same experienec here - after I upgraded to Mavericks, accessing the internet from my iMac has slowed down to the point of pain - some things never actually complete, I cann no longer watch Vimeo movies for example on the iMac.  I have a steam-driven laptop with WinXP an iPad and IMac, they are all next to each other, they are all conneceted over wi-fi to the same router.  Speed tests show the iMac is more than 10 times slower than the other two devices.

I was also having a problem and someone on Apple's Support Communities just wrote this as a suggested fix.  I did it and no longer have any issues and my internet is no longer slow.

HERE IT IS;

Might be corrupted network preferences ...

Open the Finder. From the Finder menu bar click Go > Go to Folder

Type or copy paste the following:

/Library/Preferences/SystemConfiguration

Click Go then move all the files in the SystemConfiguration folder to the Trash.

Turn off the base station for about ten seconds then turn it back on.

See if that makes a difference.

Your Mac will generate a new SystemConfiguration folder for you.

I'm also suffer this problem for month and about return my rMBP, and I think is the OS, cause I hook my mac mini over the ethernet and work for few minute, then just stop loading. I have 20mbs and keep have to switch on and off. Other devices work fine.

But the thing is when I brought the rMBP to my friends house. Its work perfect.

I have netgear gateway and wonder if that something doesn't work with Mac. I can't upgrade firmware.

Thanks you very much for this suggestion.  It made an immediate difference for me.  In my case I would experience similar intermittent problems whether I was on wifi or tethering through my IPhone5, and it did seem to be DNS related.

I deleted the folder as you suggested and rebooted.  Just in case I created a backup of it by going into Terminal and issuing the command:

> cd /Library/Preferences && tar zcvf $HOME/sysConfigBackup.tgz ./SystemConfiguration

then deleted it:

> sudo rm -rf /Library/Preferences/SystemConfiguration

I noticed when it restarted that the list of network services was reset to have only wifi and thunderbolt ethernet.  My list of known wifi SSIDs and credentials were also reset.  These are the only caveats I would add for this solution, but I'm ok with it since it worked for me!  Thanks again!

Because it's an iMac, I'm assuming that you're using the bluetooth keyboard and possibly a trackpad or bluetooth mouse.

If this is the case and you're only having the problem when connected via Wi-Fi, you may be experiencing interference.

Bluetooth runs at 2.4ghz, Wi-Fi routers can run at either 2.4ghz or 5ghz.

When I installed Mavericks on my iMac, wireless speeds took a dive and it took me a lot of troubleshooting to figure out.

It was a strange problem because I hadn't changed my network at all and out of 3 devices connected to it, the iMac was the only one having speed issues on Wi-Fi; and only after installing Mavericks. It was working fine the day before under OS X Snow Leopard.

Give this a try:

• Option-click on Wi-Fi in the menu bar.
• Go to 'Open wireless diagnostics'. (You may have to enter your admin password)
• Ignore the introduction window that pops up and instead go to 'Window > Utilities' in the menu bar. (alternatively press ⌘-2).
• Click on 'Wi-Fi Scan'.
• Click 'Scan Now'.

This will show you all of the wireless networks in your area, what channel they're on, and the band (2.4ghz or 5ghz).

• If your wireless network is using the 2.4ghz band, change the broadcast channel in your router settings. (You'll have to refer to your router's manual if you don't already know how to do this).
• Choose a channel that is different than the channel you are currently using and also different to the other wireless networks in your area.

This may not be a fix for everyone, but it solved a wireless problem that had been plaguing me since installing Mavericks.

thanks boxx,

your solution also worked for me

thanks codybrianna.  i was having issues regardless of the browser i used. works perfectly now.

Great!  Love your picture.  I have had three Westies.

This worked for me!  Thanks a million!  Rockin fast right now and I didn't have to do a bunch of fancy pants tech stuff.  Pretty easy.

I am having this problem, but I'm not using Wi Fi.  I am using a wired network.  The problem started as soon as I installed Mavericks.  Sometimes the internet is fine and runs at full speed and sometimes mail and safari and all internet runs very slow or not at all.  Tried some of the suggestions here that apply to non-wifi setup. 

The problem is still happening.  I have other computers connected to the same network and they are not having any difficulty accessing the internet.  This problem is isolated to this Mac Pro.

Update:  Disabled Intego Netbarrier anti-virus and suddenly my internet is working again.

Related or coincidence?  Time will tell.

Intego Netbarrier.

Netbarrier.

A barrier to the internet...

Could be that.

If you prefer to have something like that running, I would check through the preferences to make sure that it's not putting up a firewall where it shouldn't be.