macOS 26 breaks custom DNS settings including .internal
gist.github.com
March 19, 2026
5 min read
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Summary
macOS 26.3.1 introduces a bug that breaks supplemental DNS resolution for custom TLDs in the /etc/resolver/ configuration. This issue is a regression from the previous version, macOS 25.x 26.3.0, which functioned correctly.
Key Takeaways
- macOS 26.3.1 has a regression that breaks the /etc/resolver/ mechanism for custom TLDs, which worked correctly in macOS 25.x.
- The mDNSResponder in macOS 26 intercepts queries for custom/private TLDs and does not consult the specified unicast nameserver, leading to failures in local development and private network DNS workflows.
- Tested TLDs that are affected include .internal, .test, and .home.arpa, all of which fail to resolve correctly in macOS 26.
- The issue results in applications using getaddrinfo() failing to resolve custom domains, returning "Unknown host" errors instead.
Community Sentiment
Positives
- Using *.localhost for local web development simplifies DNS management, allowing for easier access to local resources without additional configuration, which can enhance developer productivity.
Concerns
- macOS 26 introduces significant breaking changes that complicate app development, such as restrictions on brightness settings for displays, which directly impacts user experience and functionality.
- The reliance on LLMs for bug reports raises concerns about accuracy and validation, potentially leading to mistrust in the reporting process and delaying necessary fixes.