What Is Extension?
A domain extension is the suffix that appears at the end of a domain name, after the final dot. Also known as a Top-Level Domain (TLD), the extension categorizes and identifies the type or origin of the domain. Common extensions include .com (commercial), .org (organizations), .io (tech/startups), and .ai (artificial intelligence).
Extensions fall into several categories: generic TLDs (gTLDs) like .com and .net, country code TLDs (ccTLDs) like .uk and .de, sponsored TLDs (sTLDs) like .edu and .gov, and new gTLDs like .app and .xyz. There are currently over 1,500 TLD extensions available for registration.
The choice of extension significantly impacts a domain's value, perception, and functionality. A .com carries universal recognition, while a .ai signals artificial intelligence focus. The 'right' extension depends on your industry, target audience, and brand strategy.
Why This Matters for Startups
Choosing the right extension is one of the most important early decisions for your startup. The default choice is .com for maximum recognition, but sector-specific extensions like .ai (AI companies), .io (tech startups), or .dev (developer tools) can actually strengthen your brand by signaling your focus. Our TLD guides in this dictionary break down each extension's strengths, pricing, and best use cases to help you decide.
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