WiFi slowdown (or cap) on Catalina 10.15.2 - but not with SafeBoot and iPhone

As a precaution, before the EtreCheck test I removed the third party extensions Little Snitch and PreyProject (an anti-theft utility that already helped me get back my stolen Mac in 2018). However, I want to say to peter_watt that the anathema "third party extensions are no good" is not always true. I have been using LS and Prey for MANY YEARS, and they worked fine on Catalina 10.15 and 10.15.1 without ANY problems, so IMHO they won't suddenly be creating a problem.

As suggested this is the EtreCheck report, plus a screenshot of the Network section.

In addition to this, I have played around with ActivityMonitor and discovered an interesting fact: force-quitting "mDNSReponder" once after a reboot… resolves the problem completely. I did this around 2 hours ago, and a SpeedTest now gives me absolutely perfect results (screenshot nr. 2):

Now hello to the Apple moderators - TWO of my recent entries about the same problem (but with other details) within the last 24 hours completely disappeared from here. COMPLETELY DISAPPEARED as in, when you connect to the URL that you remember / had saved, it says ACCESS DENIED.

Is this CENSORSHIP or is it a GLITCH or what is it?

Anyway, since I opened a case with Apple about the mDNSResponder problem and there seem to be other people with the same issue (see here https://discussions.apple.com/thread/251014838) I am not going to step down. If whoever deleted my two previous posts continues to do so, I will continue to repost, day after day after day. THIS IS AN ISSUE.

I have re-installed all my habitual software (LittleSnitch, PreyProject and others) and can now confirm:

• after a reboot, speeds are low as previously described
• force-quitting "mDNSReponder" once after reboot (inside ActivityMonitor) resolves the problem completely., i.e. gives me back normal WiFi speeds with rates that touch almost 100% of what my LTE can deliver.

After a quick search here and on Google I discovered that "mDNSReponder" has a long history of failures and successes. This story here seems to confirm it is still one of Apple's biggest problem zones.

Why should I get rude…???

I habitually have Little Snitch installed (see here) to protect me from things connecting to other things on my machine without me knowing it. But of course the very first thing I did when this started to occur was to disable it. I still have CleanMyMac installed (latest iteration, paid version) but nothing else that leaves traces deep inside the system.

Still not getting why I would get rude…

Thanks for still getting back to me with this! When I said "third party" I meant apps that plant extensions in the Library and System folders - but I get your point. However, it seems at least odd to me that now, with everything re-installed and force-quitting mDNSResponder just once after reboot, the Wifi works perfectly. Would logic not dictate (!) that, as you say, "TeamViewer, Transmit, Microsoft AutoUpdate, etc. no doubt use mDNSResponder" and therefore slow down the Wifi?

"…seeing your WiFi speed is normal in Safe Mode, that means one or more of the third-party apps when loaded in normal mode are causing a slow down" - I completely agree.

I know that force-quitting "mDNSResponder" is not really a viable solution. My problem is that I am unable to find out which one exactly causes the slowdown since Catalina's last update to 10.15.2 (because again, I had NO problem whatsoever before that). Plus, the problem does NOT exist with Ethernet - isn't Ethernet also using the mDNSResponder protocol…?

Anyway, I would pay for a software solution that can monitor the network and then tell me what exactly is slowing down my Wifi...

Maybe, but no, this is not true, this forum is FULL with post on the same issue with people calling their posts differently.

I would accept this if there were a transparent policy when a post is deleted and why it is deleted. But to just discover your forum entry has vanished into thin air is frankly unacceptable.

Dear Peter, you might be a Level 5 and have 4400 points, but when you begin a conversation with a complete stranger, aka me, and in the very first sentence you say "now don't get rude", you set the tone. I am not American (!) and I don't react well to being treated with what for me feels like "pseudo-polite passive aggressiveness". And talking about "final sanctions" does not make things any better.

But let's move on and focus on the issue at hand.

Apple Support service has called back already twice with interesting propositions to resolve the issue - that they are very much aware of. They logged onto my machine (last time 30 minutes ago) and together we went through several steps (terminal commands and more). Until now we haven't resolved the issue. But I have been told that the case is getting noticed. Of course, I will post any and all solutions and positive progress here.

Thank you, Peter.