# What YC Startups Reveal About Domain Extensions (2026)

Canonical HTML: https://domainsearchking.com/yc-startup-domain-extensions

Availability: this text is an editorial snapshot, not a current registration guarantee. Use the [live domain checker](https://domainsearchking.com/verify) or [MCP](https://domainsearchking.com/mcp) before treating a name as available. Registry errors mean unknown, not available.

Startup naming data, 2026

Updated July 6, 2026

Reviewed by the Domain Search King editorial team · Updated July 2026

.ai has genuinely overtaken .io as Y Combinator's fastest-growing domain extension. What hasn't happened is a .com decline — actual batch counts show .com flat at 48-54% for five straight years. The real story is who .ai stole share from, and it isn't .com.

## 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:

| Batch | .com | .io | .co | .ai |
| --- | --- | --- | --- | --- |
| Winter 2021 (251 cos) | 49.8% | 11.95% | 8.7% | 6.77% |
| Summer 2021 (374 cos) | 54.01% | 9.36% | 6.95% | 5.08% |
| Winter 2024 (248 cos) | 53.2% | — | — | 23.4% |
| Fall 2025 (~150 cos) | 48.7% | — | — | 32% |

Sources: [James Names (W21)](https://jamesnames.com/2021/06/data-driven-just-49-8-of-y-combinator-winter-2021-companies-use-com/), [James Names (S21)](https://jamesnames.com/2022/04/yc-s2021-demo-day-domain-trends/), [Smart Branding (W24)](https://smartbranding.com/y-combinators-winter-2024-batch-and-their-domain-name-choices/), [Smart Branding (F25)](https://smartbranding.com/y-combinators-fall-2025-batch-and-their-domain-name-choices/) — each a direct tally of an actual batch, not a modeled estimate.

### The trend, visualized

.com, W21

49.8%

.com, F25

48.7%

.io, W21

11.95%

.ai, W21

6.77%

.ai, F25

32%

.com barely moved (49.8% → 48.7%) across five years. .ai grew nearly 5x in the same window.

## 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](https://domainsearchking.com/good-ai-domain-names-taken) 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](https://domainnamewire.com/2025/08/05/new-data-28-of-y-combinator-and-techstars-startups-using-ai-domains/)). 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](https://smartbranding.com/top-private-yc-companies-by-valuation-and-their-domain-name-choices/)) — 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](https://domainsearchking.com/io-vs-com) ([Tech Startups](https://techstartups.com/2024/10/10/the-end-of-io-domains-why-tech-companies-using-io-domains-should-prepare-for-possible-disruptions/)). 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](https://domainnamewire.com/2015/08/09/paul-graham-change-your-name-get-the-com/)) — 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](https://domainsearchking.com/invented-names-vs-keyword-domains) ([NameMesh](https://www.namemesh.com/guides/domain-naming/yc-startup-domain-name-trends)), 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.

### Check Your Name Across Every Extension

Whatever extension fits your category, check it live via RDAP before you get attached to a name. Availability-first naming (this site as a [Namelix alternative](https://domainsearchking.com/namelix-alternative)) is listed under [features](https://domainsearchking.com/features).

[Multi-TLD check →](https://domainsearchking.com/domain-taken) [Read .ai vs .com](https://domainsearchking.com/ai-vs-com)

## Frequently Asked Questions

### Has .ai really overtaken .io among YC startups?

Yes. In YC's Winter 2021 batch .io held roughly 12% and .ai about 7%. By Fall 2025, .ai reached roughly 32% while .io declined sharply — a clear reversal.

### Is .com dying out among startups?

No. Actual YC batch counts show .com holding steady in a 48-54% band across five years. The share lost to alternative extensions came almost entirely from .io, not .com.

### Do investors care which domain extension a startup uses?

There's no evidence of a hard rule. Extension choice today reads more as a category signal than a red flag when it matches the product.

### Is there a risk to using .io as a startup domain?

A geopolitical one: the UK and Mauritius signed a treaty in May 2025 affecting sovereignty over .io's home territory. ICANN ties ccTLD status to a live ISO country code, so .io's long-term status carries a small, real dependency on how that plays out.

### Does the domain extension a startup picks predict its success?

No direct evidence supports that. Name brandability is better correlated with YC outcomes than the extension itself.

## Related tools & guides

[Live search](https://domainsearchking.com/) [AI domain generator](https://domainsearchking.com/ai-domain-name-generator) [AI business names](https://domainsearchking.com/ai-business-name-generator) [AI agency names](https://domainsearchking.com/ai-agency-name-generator) [Shopify names](https://domainsearchking.com/shopify-name-generator) [Namelix alternative](https://domainsearchking.com/namelix-alternative) [AI taken rescue](https://domainsearchking.com/ai-suggested-domain-taken) [Domain taken?](https://domainsearchking.com/domain-taken) [Verify a domain](https://domainsearchking.com/verify) [Hallucination index](https://domainsearchking.com/ai-hallucination-index) [Invented vs keyword](https://domainsearchking.com/invented-names-vs-keyword-domains) [Catchy ideas](https://domainsearchking.com/catchy-domain-name-ideas) [One-word .coms](https://domainsearchking.com/available-one-word-domains) [How to choose](https://domainsearchking.com/how-to-choose-a-domain-name) [How to check taken](https://domainsearchking.com/how-to-check-if-a-domain-name-is-taken) [MCP for agents](https://domainsearchking.com/mcp) [Niche ideas](https://domainsearchking.com/ideas) [Features](https://domainsearchking.com/features) [About](https://domainsearchking.com/about)

Statistics cited from independent batch-count analyses and registry data as noted above. Domain Search King is not affiliated with Y Combinator, Identity Digital, or any registry.