What Recent YC Startups Reveal About Domain Extensions

The Actual Batch-by-Batch Data

Instead of relying on a single headline stat, here's what independent counts of actual YC demo-day companies show across five years:

Sources: James Names (W21), James Names (S21), Smart Branding (W24), Smart Branding (F25) — each a direct tally of an actual batch, not a modeled estimate.

Why .ai, Why Now

The shift isn't founders settling for .ai because .com is scarce — it's a deliberate category signal. Registry data from Identity Digital (which operates both the .io and .ai backends) found 28% of YC and Techstars startups used .ai domains in the first half of 2025, up 7 percentage points from the year before, with .ai usage up roughly 300% since 2020 (Domain Name Wire). Worth disclosing plainly: Identity Digital runs the registry for both extensions and has a direct commercial interest in this narrative — the batch-level data above from independent trackers corroborates the direction, but treat Identity Digital's own framing as informed, not neutral.

Reality Check: .com Isn't Dying

Every actual batch count shows .com holding in a 48-54% band across five years — essentially flat. A frequently cited "46% all-time average" figure makes .com's decline look more dramatic than it is, because it blends in YC's earliest 2005-2008 batches, when .io/.ai/.co barely existed as cultural options — of course .com was near 100% then. That's survivorship bias, not a recent trend. Among YC's highest-valuation historical companies, 88% (251 of 284) still use .com (Smart Branding) — not the "100%" figure sometimes repeated, but still the clear majority.

The .io Wildcard

Part of .io's decline may not be about .ai's appeal at all. In October 2024, the UK agreed to transfer sovereignty of the Chagos Archipelago — the British Indian Ocean Territory that .io is assigned to — to Mauritius, with a treaty signed in May 2025. ICANN ties ccTLD status to a live ISO country code; if the BIOT code is retired, .io becomes eligible for retirement under ICANN's own policy. With roughly 1.6 million .io registrations against Mauritius's own .mu registry holding only about 24,731, a full shutdown looks unlikely — but domain holders currently have no guarantee of long-term continuity (Tech Startups). Some of .io's founder exodus may be quiet risk-aversion, not just .ai's pull.

Does It Matter to Investors?

Paul Graham's often-quoted 2015 line — "the problem with not having the .com of your name is that it signals weakness" (Domain Name Wire) — predates the .ai wave by a decade. There's no verified study tying domain extension choice to funding outcomes independent of company age and category. The more defensible read: extension is a signal of category and era, not a cause of success. A claim like "72.8% of investors say a single-word .com helps significantly" is circulating in some domain-industry content but traces to no identifiable named study — treat it as unverified.

What Actually Predicts Success (Hint: Not the TLD)

The more consistent, 20-year-stable pattern across YC data is name brandability — roughly 87% of YC startups pick brandable, invented, or arbitrary names rather than descriptive ones (NameMesh), a pattern that holds regardless of which extension they land on. Extension choice is a category-fit decision. Brandability is the naming decision that's actually correlated with the crowd you're trying to join.

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