Slow wifi after Big sur update

Hi! I'm glad I found this thread. I'm having exactly the same issue. Running macOS 11.1 (20C69) Wifi speeds are much slower (only one third or one half of the speed on all my other devices). But the strange thing is: It happens only after some time. Directly after reboot I get full speed of 500-600mbps. But then after 5 to 10 minutes I'm only getting about 150-250mbps. Then nothing can bring back the faster speeds.

Tried everything:

• resetting PRAM/SMC
• completely removed wifi adapter under network settings and added new one
• removed wifi preferences
• I'm not using any firewall/antivirus-software
• changed wifi 5ghz channels, MTU size, CTR threshold
• optimized all settings on my router
• killed all background processes and unnecessarily running apps
• disabled timemachine backup

Nothing is working. But all other apple devices in this house (two iPhone 11 Pro, iPad Pro and so on) get 500-600mbps very single speedtest. Just my mac doesn't get the full speed. And honestly this was by far the most expensive Apple product I've ever bought (2849€). So that's driving me crazy...

We need a fix for this problem!

Guys I think I may have found a solution for this problem.

1. Turn off bluetooth.
2. Disconnect all peripherals from your computer.
3. Open System Preferences. In the "Energy Saver" preference, de-select "Wake for network access" (no check, and leave it that way).
4. Open the finder. Select the "Go" menu. Select "computer." Select "Macintosh HD." Go the the "Library" folder. Go to the "Preferences" folder. Find the preference file "com.apple.bluetooth.plist."
5. Rename "com.apple.bluetooth.plist" as "com.apple.bluetooth.plist.old" (i.e. add ".old"). Eventually, if this solution works for you, you can delete this "old" preference file.
6. Restart your computer (this will create a new "com.apple.bluetooth.plist" preference file).
7. Turn bluetooth back on.

Apparently, the problem is a bug caused by a bad interaction between the bluetooth preference file and wifi.

Hey jens8553b,

We're glad you thought to ask Apple Support Communities about the slow network speeds you're experiencing after installing macOS Big Sur. We want to help! You've completed some great steps so far, so let's see if we can narrow it down further. If you haven't already, use Wireless Diagnostics to see if it reports: Use Wireless Diagnostics on your Mac

To help isolate and narrow our focus we'll also want to test this while using safe mode, a new user account, and macOS Recovery. Safe mode will tell us if a third-party app is possibly causing this to happen. Here's more information on safe mode and how to start there: How to use safe mode on your Mac

After noting the results of safe mode, restart your Mac normally to exit, and we'll then create a new user account to test. Please do not use the Guest account. This will let us know if the issue is with your account only, or system-wide: Set up users, guests, and groups on Mac

After noting those results, we'll start to macOS Recovery and use the option to Get Help Online. This takes macOS completely out of the equation: About macOS Recovery on Intel-based Mac computers

Keep us posted on the results.

Take care.

Jens,

That's good to know. What happened in the test user account, and did Wireless Diagnostics report any issues? You may consider creating a new network location to see if settings there are causing this: How to use network locations on your Mac

Also, since the speeds pick up in safe mode, check the steps under "If the issue doesn't continue in safe mode" here: How to use safe mode on your Mac

Keep us posted.

Jens,

Great information! With the alerts you're seeing in Wireless Diagnostics, use the following resource to help with the settings for your wireless router. You may also need to work with your internet service provider for help with the settings: Recommended settings for Wi-Fi routers and access points

Let us know how it goes.

Cheers.

UPDATE:

So, I was able to get a USB C to HDMI adapter with better shielding and I stayed on 11.2.3 and my internet jumped to 100 mbps download.

Granted that is still not as fast as my iphone 11 which is setting right next to my M1 mac mini and it's getting 300 mbps download.

Then, I decided to update today to 11.4...do'h!

Now my internet is right back to 8-10 mbps...wow.

I tried the solutions above with the bluetooth plist fle but that did not work for me.

Then I tried waht "blujez " recommended and I

1. 1. turned off my bluetooth,
   2. turned off my wifi,
   3. turned wifi back on,
   4. turned bluetooth back on...
   5. internet is now back to 100 mbps, go figure.

I have no idea why that worked but I'm going to leave it alone for now because I do not feel like downgrading to 11.2.3 again.

Hi,

I can confirm that the issue is still there with Big Sur 11.2. And I am 100% sure that the issue only happens in Big Sur.

I did a lot of testing, changed the Channel of 5GHz Wifi, optimized all settings, wrote with netgear support and double-checked everything. None of my other devices is having issues. So I decided to test if it's an hardware-related or software-related problem.

So I just installed macOS Catalina to an external USB drive and started testing.

Here are the results (I did two days of testing):

In Catalina I constantly get 450-600Mbit/s of download speed:

And on Big Sur I get 600 Mbit/s as well, for the first minutes after rebooting. But then - say after 15-20 Minutes, or after waking up from standby - I only constantly get half of the download speed, only 250-300 Mbit/s:

This is so mysterious. I repeated the speedtest many many times and the MacBook Pro from 2018 was on the exact same position on my desk, right next to the Orbi RBS50 Satellite and connected with 5Ghz to the same BSSID. The T/x rate is at 866Mbit/s, even when getting the "low" download speeds.

This absolutely is an evidence for me that the problem is either correlated to Big Sur or any other Software issue. But as I said, I tried everything (new user account, removing Wifi .plist and bluetooth .plist files, creating new network location, removed SCM/PRAM, I don't have any antivirus or firewall installed, Wireless diagnostics didn't found anything, and so on and so on...).

Also the problem only exists on Wifi, I get full speed over ethernet. Also when pinging for example google.com on wifi, I get a spike or some drop-outs, so the wifi connection isn't stable.

I am happy for any help or feedback!

Since I have instaled Big Sur last week on my iMac (Retina 4K, 21.5-inch, 2017) I have moved from an ethernet connection that had 800Mbps to 200/250Mbps on a 1Gb/s network.

I have a MacBook pro 15 (early 2011) that is not running Big Sur and the ethernet connection is still on the 800Mbps.

This issue 100% sure related with Big Sure and Apple is looking sideways and trying to point in different directions instead of looking to the actual cause (Big Sur) on this issue reported by many many users!!!

I had a perfectly working ethernet connection and with screenshots to prove it from the before and after big sur.

Before:

After:

Big Sur changed the ethernet connection, nothing else!

I have the same issue. In my case, I bought the M1 (upgraded from MacBook Air 2013 running on High Sierra). The file transfer speeds over the network have drastically reduced when on WiFi. The same issue doesn't happen with ethernet. Tried all the possible tweaks adjusting the Wifi 5Ghz channels and width on the router but no change in the file transfer speeds at all.

I tried everything above with Apple tech, with no resolution of my problem. I'm getting ~8-10 Mbps download speeds on my MacBook w/Big Sur and ~100Mbps on my other macs running Catalina. This is a glitch that has occurred after updating from 11.01 to 11.1.

Yes! Thanks for confirming. That’s driving me crazy. The device that was the most expensive by far only has one third of the download speed of all my other devices... very very disappointing. Hoping for Big Sur 11.2