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I own a MacBook Pro for some months now, it came with OS X Lion pre-installed. Since then, surfing the net with it is painful due to slowness. I also have a MacBook with Snow Leopard on it, there the internet works at normal speed. Based on this I conclude the problem is inside the MacBook Pro - it shows full WLAN connectivity but loading Google takes forever. My Router is a AVM Fritz!Box.

What I tried so far to optimize the speed - unless (noted) the changes made below don't affect the measured latency or speed at which pages render:

  • Resetting the router, turning WLAN on and off
  • Switching WLAN channels, trying 802.11n+a and 802.11n+g
  • Deleting all Wi-Fi networks in the system preferences
  • Resetting PRAM and NVRAM
  • Re-starting the MacBook Pro multiple times in a row
  • Disable iCloud in system preferences
  • Using another Browser than Safari
  • Renaming the network
  • Disableing "Use channels optimized for 300 Mbit/s" in my router (this helped, but still not to equal the speed of Snow Leopard)

What else could I try? I read changing the DNS server Google's can help, bit to my understanding, this really can't fix the problem. Reinstalling is not an option. I am really desperate to solve this problem because it is more than annoying!

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Is this happening on the Ethernet too? or just the Wifi? – iGameRam Jul 6 '12 at 14:48
Thanks for you comment! It's just with the wifi. And just a note: I asked this question in march and even now I haven't found a solution for it! – Sven Jul 6 '12 at 14:52
Did you try to reinstall OSX (clean install) and try. If you can't find a solution then i guess it may be a Wifi radio hardware issue, i hope you are still under warranty. Please do check if the problem persists with some other Wifi Router too. – iGameRam Jul 6 '12 at 15:06
With other Wifi routers it's fine. It's just because I have an AVM FritzBox. Lion doesn't work with them smoothly. It's know issue but Apple/AVM won't fix it. – Sven Jul 6 '12 at 15:08
My laptop is extremely slow, right out of the box, it is very frustrating, can't stream radio or even browse the internet, that is crawling. I will try another browser, Chrome, but it seems ridiculous that a new macbook air right out of the box, would crawl on the internet. I have 4 wi-fi bars and had decent speed on an older machine. I'm not sure what to try. – user27038 Aug 8 '12 at 16:18

Have you tried flushing the DNS cache? In, enter dscacheutil -flushcache.

It could be your DHCP router handing out IPv6 information incorrectly, which is especially annoying if you don’t need IPv6 — like at home. This seems like the most logical explanation, given that all browsers and applications are suffering from the speed issues.

Go to System Preferences → Network → WiFi → Advanced → TCP/IP and set “Configure IPv6” to “Link-local only”.

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Thanks for your reply, I've done both things you suggested above. The internet still works somehow, although I do not know if it is really faster than before. The MacBook running Snow Leopard is still noticeably faster. – Sven Mar 25 '12 at 20:15

Since this issue has been outstanding for months and you have done a very good job of ruling out the easy sources of slowness, you are now faced with digging in and doing some measurements as well as spending more time isolating the issue.

These things are very helpful for next steps:

  • isolating the OS as installed
  • taking the Macs to a different router and re-testing
  • reinstalling the OS (I know you said it's not an option, but it is for many and may be the cure you need if you have a driver problem or other corruption on the OS install)

Before you do anything, you will want to get accurate timing of three web sites that you care to optimize for. Since you say everything is slow and it's taking forever, you could use a stopwatch to time things. I prefer using the web inspector in Safari to get millisecond accurate timing of the elements that make up a page load.

Google in Web Inspector - Wi-Fi

You get to this by the settings, advanced tab and enabling the checkbox that places the Develop menu in the menu bar. Here (above) you can see a reasonably fast wireless network with a fairly good broadband connection to the internet. Below you can see the same page when loaded over 100 MB ethernet - significantly faster load time and less latency.

Google in Web Inspector - ethernet

Once you have a feeling for what slow actually measures to be, you can know if it's a latency or routing or bandwidth issue.

Now you can change one thing at a time (the OS, the router, whatever) and re-measure to see if you have made things better.

I would install Lion cleanly onto an external drive and test that. It's possible your router and Mac just don't work together well, but I would expect you could tune things well enough with these tools to resolve the issue. Once you have the details of a page load, you'll know if the same content is begin drawn to both OS and where to look for improvements. Don't neglect free RAM as well - if your Mac can't cache items well due to space issues, you could simply be re-downloading things from the internet on the "slow" machine.

Good luck hunting.

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One tip I found on the German Apple Support Community actually solved my problem: I disabled WiFi 802.11n, so went with 802.11bg. Since then, my speed is comparable to Ethernet again. I am suggesting this because you do not seem to have tried that. WiFi 802.11n is the fastest WiFi standard, so it hurts to switch it off. But WiFi b+g is faster than my internet anyway.

(After posting my initial answer sometimes the WiFi was fast, sometimes slow, sometimes unusable, sites would wait to load forever. That is the reason why I voted to delete my initial answer, because it did not actually solve my problem.)

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