The extension is not just decoration. It changes how the name feels, how easy it is to remember, and how much authority the brand carries before anyone sees the product.
.com is the default trust layer
.com still feels like the default home for a serious company. It is easiest to remember, easiest to explain, and least likely to leak traffic to someone else. If the budget allows it, the matching .com is usually the cleanest long-term asset.
.ai is a category signal
.ai tells the market what the product is about immediately. That is useful for AI tools, data products, automation platforms, and machine-learning education. The risk is narrowness: if the company expands beyond AI positioning, .ai can feel like a campaign domain rather than the main brand.
.io fits technical audiences
.io remains familiar to developers and SaaS buyers. It works well for APIs, dashboards, infrastructure tools, and technical products. It is less ideal for broad consumer brands where people expect .com.
.co and .so are compact startup choices
.co works for commerce, startup, and company-style names. .so can make short words feel modern and lean. Both are useful when the root is strong, but they usually need cleaner spelling than a .com because the extension is doing less trust work.
The practical rule
Buy the extension that matches the first real use case, but do not ignore the second use case. A developer tool may start on .io, but if the company plans to become a large SaaS brand, the .com becomes important sooner than expected.