Extension Domains
Secondary domains used to reach topical or query space a main domain cannot credibly occupy. Attributed to Koray Tuğberk Gübür, 2026.
What it actually means
A domain accumulates a topical identity, and that identity has edges. A site established as an authority on one subject often cannot extend credibly into an adjacent one, because the entity it represents does not plausibly cover both.
Extension domains answer that by building a separate property with its own identity for the adjacent space, rather than stretching the original past what it can support.
The legitimate and illegitimate versions
The legitimate version is a real publication with its own editorial purpose, serving readers who would want it independently. Large media groups have done this for a century.
The illegitimate version is a shell that exists only to point at the parent, which is the tactic the same practitioner named separately as Wasteful Domains. The test is whether the property would still make sense if the parent did not exist.