The extension after the dot is part of your brand whether you like it or not. Here's the honest read on the four that matter most.
.com — the default that still wins
.com is what people type when they're not paying attention, which is most of the time. If you can get it, get it. It's the safest choice for any business that sells to a general audience.
.io — the developer shorthand
Born as the British Indian Ocean Territory ccTLD, .io became shorthand for “input/output” and now reads as a tech or developer product. Great for tools and APIs, slightly alienating for a bakery.
.ai — the moment's favorite
.ai exploded alongside the AI wave. It's a clear signal if your product genuinely leans on machine learning — and a little try-hard if it doesn't. Registration and renewal also cost more than most.
.co — the graceful fallback
When the .com is gone, .co is the least jarring substitute. It's short, it reads as “company,” and it's only one keystroke from the default.
The rule of thumb
Buy the .com if you can. If you can't, pick the extension that matches your audience, not the one that's cheapest. You can compare a name across every extension at once on the Domain search page.