Corrected 9:01 a.m. PT: Medium is only launching this feature in “limited beta.”

Starting today blogging service Medium will allow select users to create their own “publication” with a custom domain.

For the launch, Medium highlighted a handful of examples: New AmericaMidcentury ModernSubstance, and The Nib (one of Medium’s in-house blogs). More, from Medium:

We want to make sure we’ve got the kinks worked out before we roll this out more widely. If you are interested in hosting your publication at a custom domain, let us know here, and we’ll update you when we have more information to share.

The new feature turns Medium into a far more formidable competitor to and Tumblr — this is particularly interesting when you consider Medium’s interest in replicating aspects of Tumblr’s feature-set.

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Ultimately this is part of a huge shift for Medium, as it evolves from designy blogging tool to social publishing platform.