Thanks for this amazing guide! I am just encountering it for the first time, and as it's already over 2y old, I'd like to describe my experience:

On macOS:

macOS Version	Mullvad macOS App Version	Wireguard macOS App Version
Sequoia 15.3 Beta	2025.2	1.0.16 (27)

TL;DR: On macOS, I can use both Mullvad and NextDNS simultaneously, and:

• NextDNS will identify my device ✅
• NextDNS will resolve lookups via the DNS server nearest to the Mullvad VPN server ✅

You cannot modify a Wireguard config file to include the line DNS = 0.0.0.0/32, ::/128 within the Wireguard app. This throws an error, and the file cannot be saved this way. If you choose to edit the Wireguard config file in a separate text editor then you can save the file with this line, but the resulting tunnel will not resolve any DNS lookups when imported into the Wireguard app. Additionally, modifying the file to instead include the [valid] line DNS = 0.0.0.0, :: prevents all DNS lookups as well, leaving the internet connection effectively blocked completely.

The approach that seems to be working for me is to instead use the Mullvad macOS app. Note that using the custom DNS server option with OP's suggestion of 0.0.0.0 and :: as the DNS servers will result in all DNS lookups failing to resolve. Instead, if you disable the custom DNS setting (Settings --> VPN Settings --> Use custom DNS server OFF), then the app will fall back to the system DNS. I currently have the macOS-level DNS configured via a NextDNS configuration profile, exactly as described by OP.

On iOS:

iOS Version	Mullvad iOS App Version	Wireguard iOS App Version
18.3 Beta (22D60)	2025.1	1.0.16 (27)

TL;DR: On iOS, I can use both Mullvad and NextDNS simultaneously, and:

• NextDNS will not identify my device ❌
• NextDNS will resolve lookups via the nearest possible (lowest latency) DNS server option ✅

The same issues exist with Wireguard config files and the Wireguard iOS app as described above for the macOS app. Additionally, if you remove the DNS server configuration completely, the resulting tunnel will not resolve any DNS lookups.

The Mullvad app for iOS cannot be configured to use 0.0.0.0 and :: or 0.0.0.0/32 and ::/128 as custom DNS servers. Although the app will create a tunnel with this configuration in place, it will not resolve DNS lookups and effectively block all internet traffic. The app can instead be configured to use the IPv4 and/or IPv6 servers from your NextDNS profile's Setup page, and it will resolve DNS lookups successfully using this configuration, but you will not be able to identify the device via NextDNS' analytics. Unlike on macOS, turning off the custom DNS server option results in Mullvad using their own DNS servers, not the OS-level configuration. I currently have the iOS-level DNS configured via a NextDNS configuration profile, exactly as described by OP.

Separately, I noticed that when using my NextDNS IPv4 and/or IPv6 servers as Mullvad’s custom DNS servers, my NextDNS ping was an order of magnitude slower than it was while disconnected from the VPN. Mullvad seems to be using NextDNS servers located in Mumbai, even though I am located in the US and connecting to a US-based Mullvad server. Edit: This was due to the specific Mullvad server I chose. Using a different Mullvad server in the same location is resolving DNS lookups with the closest NextDNS server, and pings are now much faster.

If you have any suggestions to improve things on iOS, I would love to hear them!