`.internal` and `.local` are safe and won't be used in the future. There are reserved for internal networks
Re:New gTLD Application for .lan
by john_strinlai on Thursday October 08, 2026 @12:48PM
(#50008241)
while .local is reserved, it's reserved for mDNS, and should be avoided on things like active directory. using an internal subdomain of a registered public domain is best practice. .internal is also okay.
Even today when setting up greenfield networks, I generally use internal.company.com. It also lets you get public trusted SSL certificates so you don't have to deal with internal PKI.