Choosing a TLD: Why .com Is the Default and What Else Works
The ending of a domain name, the TLD, is the first thing the name check looks at. It is also the part of a name that is easiest to get wrong, because a good name on a poor ending can be harder to use than an average name on .com.
Why .com is treated as the standard
In the name check, .com passes without comment: it is the ending international buyers and visitors expect, and it is the one people type by default when they hear a name.
Some other endings, such as .io, .co, .ai, .dev and .app, are treated as a second choice. They can make sense for particular industries, but they are less liquid and less familiar than .com, so the check recommends taking the .com if it is available.
Country-code endings
Endings tied to a single country, such as .kr, .jp, .cn or .ru, are flagged more strongly. Search engines treat country-code endings as aimed at that country, which limits reach in other markets, and some of them come with registration requirements or restrictions on resale.
If your audience is in one country and you intend to stay there, a country-code ending can be the right choice. The name check is written from the point of view of an international English-language market, and it says so.
Unusual endings
Endings such as .xyz, .online, .site, .info, .biz, .club, .shop and .store are judged cautiously. The reason given is buyer trust: names on these endings are harder to sell on and are more often read as less established.
What to do if the .com is taken
Try a variation that keeps the idea but changes the shape: add a topic word, change the order of the pieces, or choose a different coined word. A shorter, easier name on .com is usually a better trade than the first-choice name on a weaker ending.