mDNSResponder on Mac: Fix mDNSResponder High Network/CPU

 While in Activity Monitor, you may find the mDNSResponder process using excessive network traffic or consuming high CPU resources. Wondering what it is and how to fix it? This article got you covered.

What is mDNSResponder on Mac?

mDNSResponder (multicast DNS responder) is a background process that enables your Mac to detect other devices on the local network and communicate with them. It also manages DNS requests for services that need an internet connection.

mDNSResponder is an essential part of the Bonjour networking protocol, which allows devices on a network to automatically connect to each other, without any configuration. The mDNSResponder process will scan your local network on a regular basis for other Bonjour-compatible devices.

This process is how your Mac can automatically discover devices like printers, external storage devices, iPhones, iPads, and other computers, etc, and facilitate features that rely on auto-discovery, such as file sharing, screen sharing, iTunes library sharing, remote desktop, AirPlay, Handoff, or continue camera.

Apple removed the mDNSResponder process for Yosemite and replaced it with discoveryd in 2014 because of its high network usage. But It was brought back a year later for El Capitan, as its absence has caused a lot of issues on Mac.

How to fix mDNSResponder high network/CPU on Mac?

Sometimes, mDNSResponder may occupy high network traffic or cause high CPU usage for a short time. But if it keeps having issues, it may slow down your WiFi speed or result in loud fan noise or overheating. To fix the mDNSResponder high network/CPU issue, you can try the following solutions.

Kill mDNSResponder in Activity Monitor

Killing the macOS mDNSResponder process is a common way to resolve issues with mDNSResponder. It's especially helpful for fixing the mDNSResponder high network traffic problem. Note that this doesn't disable mDNSResponder, as it will restart immediately because your Mac needs it.

But this temporary termination can refresh mDNSResponder and hopefully calms it down.

Check if mDNSResponder stops hogging the CPU or uses excessive network traffic. If it doesn't work. continue with the other solutions below.

Reboot your Mac

Restarting your Mac can close all running processes, clear out the RAM, and reload the operating system, which may be able to fix issues with mDNSResponder. If you have external peripherals like a printer attached to your Mac, pull them out before rebooting your Mac. You can plug them back in later.

Boot into Safe Mode

Sometimes, third-party software is the culprit rendering mDNSResponder not functioning correctly. To troubleshoot it, you can boot your Mac into Safe Mode to isolate third-party applications. If mDNSResponder works properly in Safe Mode, you can restart normally.

Disable mDNSResponder

If the issue persists, you can disable mDNSResponder in Terminal and reenable it. Normally, it's not recommended to turn off a system process like mDNSResponder, as it will certainly affect your Mac's operation. But you can disable and reenable it if encountering problems with mDNSResponder.

It's worth mentioning that you need to disable SIP (System Integrity Protection) before you can stop mDNSResponder from running.

Share this post if you have managed to get rid of the mDNSResponder issue on Mac.