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What is Mdnsresponder? Why is it running on my Mac?

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  • 3 min read

If you are the curious type and find yourself opening the activity monitor on your Mac, you might have looked at a process called Mdnsresponder running under the network tab. 

At first glance, you might be under the impression that the process is malicious as it would have sent and received a lot of data in the form of packets. So what is the Mdnsresponder? Is it dangerous, or is it something useful? 

Well, in this article, we will look at the Mdnsresponder in detail and understand why it is running on your Mac.

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What is Mdnsresponder?

The Mdnsresponder or multicast DNS responder is a network-based process that is created by Apple. So if you thought that the process was malicious, you could keep all your worries at bay. 

The process is part of the Bonjour protocol, which is a zero-configuration open-source networking service. All in all, this protocol helps Apple devices to communicate with other devices on a local network without any configuration. 

So if you want to connect to a printer or share files to a network storage device, the Mdnsresponder is working in the background, making things possible. 

Why is Mdnsresponder running on your system? 

For communication between two devices, both devices need to follow the same rules for device identification and communication. 

In Apples’ case, devices on a local area network use the Bonjour protocol to identify and configure devices. After the devices are identified and configured, data is transmitted between devices using the Internet protocol. 

If you have installed Itunes on your Windows system you will see Mdnsresponder.exe running in your task manager. This helps Windows devices with Itunes library sharing and shows that the process can be found on devices other then Apple devices. 

For data to be transferred over the Internet protocol, the communicating devices need to know each others IP addresses. Over the Internet, this process is carried out using DNS servers. In the case of Bonjour, this task is done using the Mdnsresponder. 

Also read: Can your WiFi get hacked? Is sharing WiFi passwords a bad idea?

How does Mdnsresponder work?

Let’s say you want to send files using Airplay from your laptop to your mobile. The laptop starts looking for other devices on your local area network for this data to be transferred. To do this, the Mdnsresponder sends multicast DNS requests to all the devices on your network. 

What is Mdnsresponder? Why is it running on my Mac?

If a device(your phone) on your network is running the Bonjour protocol and has the same name as that in the DNS request, it would receive this request and send its IP address to the host. Once the laptop has this data, it will start transmitting data using the Internet protocol. 

Should you stop Mdnsresponder

Although the Mdnsresponder is critical for communication to occur over a local area network, you can terminate the process in the activity monitor. That said, the process would start again as it is a part of a critical networking protocol. 

Apple tried to remove the Mdnsresponder responder in 2014 in Mac OS Yosemite, and there were many bugs reported due to this change. Therefore Apple brought the process back in Mac OS El Capitan, and it fixed over 300 bugs. So it’s safe to say that you should not terminate Mdnsresponder.

Also read: Ubuntu task manager: Everything you need to know

Nischay Khanna

Nischay Khanna

A tech enthusiast, driven by curiosity. A bibliophile who loves to travel. An Engineering graduate who loves to code and write about new technologies. Can't sustain without coffee. You can contact Nischay via email: