.io vs .dev vs .app: The Developer TLD Showdown

## .io vs .dev vs .app: The Developer TLD Showdown Three domain extensions dominate the developer and tech startup space: .io, .dev, and .app. If you're building software — whether a developer tool, web application, API, or SaaS product — you've probably considered all three. This guide breaks down every meaningful difference so you can make a confident decision. Use TLD Comparison Tool to see real-time availability across all three for your chosen name. ## Origin Stories Understanding where these TLDs come from matters more than you might think. ### .io — The Accidental Tech Standard .io is the ccTLD (Country-Code Top-Level Domain) for the British Indian Ocean Territory (BIOT), a group of small islands including Diego Garcia, home to a joint UK-US military base. The territory has no permanent civilian population. In the 2010s, registrars began marketing .io to tech companies as shorthand for "input/output" — a programming concept. The rebrand worked. GitHub launched github.io for project pages in 2008. The YC ecosystem adopted it heavily. By 2015, .io had become the default alternative to .com for developer tools. There's a geopolitical wrinkle: Mauritius has long claimed sovereignty over BIOT, and the International Court of Justice issued an advisory opinion in 2019 supporting the Mauritian claim. If the territory is ever formally transferred, the .io extension could theoretically be retired. This risk is real but considered low probability by most domain experts. The Domain Registrar Infrastructure supporting .io is well-established regardless of the political situation. **Registry operator:** Internet Computer Bureau (ICB), a private UK company **WHOIS accuracy:** Required, enforcement moderate ### .dev — Google's Developer Domain .dev is a New gTLD delegated to Google in 2015 and opened for public registration in 2019. Google operates it through their Google Registry division, the same operation that runs .app, .how, .soy, and others. The key technical fact: .dev is included in the HSTS preload list, meaning all browsers enforce HTTPS on .dev domains by default. You physically cannot serve unencrypted HTTP on a .dev domain — it will fail in all major browsers. **Registry operator:** Google Registry (Charleston Road Registry Inc.) **WHOIS accuracy:** Standard gTLD ICANN requirements ### .app — Also Google, Also HTTPS-Required .app follows the same structure as .dev — Google-controlled New gTLD, HSTS preloaded, HTTPS mandatory. Google acquired the .app registry rights in 2015 for $25 million, outbidding Amazon and others. The distinction from .dev is semantic positioning: .app implies a software application (often consumer-facing), while .dev implies a developer-focused resource. **Registry operator:** Google Registry (same as .dev) **WHOIS accuracy:** Standard gTLD ICANN requirements ## Head-to-Head Comparison ### Technical Factors | Factor | .io | .dev | .app | |--------|-----|------|------| | HTTPS Required | No | Yes (HSTS) | Yes (HSTS) | | SSL/TLS Certificate cert required | No | Yes | Yes | | Registry stability | Private company | Google | Google | | Geopolitical risk | Low-moderate | None | None | | DNSSEC | Available | Available | Available | | IDN support | Limited | Yes | Yes | The HTTPS requirement on .dev and .app is worth emphasizing. From day one, your development environment and production deployment both need valid SSL/TLS certificates. For most modern projects using Let's Encrypt or Cloudflare, this is zero additional friction. For legacy systems or unusual deployment environments, it's a real constraint. ### Pricing (2026) | Extension | Cheapest Registrar | Average | Renewal | |-----------|-------------------|---------|---------| | .io | Namecheap ~$28 | $35-45 | Same | | .dev | Google Domains ~$12 | $14-18 | Same | | .app | Google Domains ~$14 | $16-20 | Same | .io costs roughly 2-3x more than .dev or .app. Over 5 years, that's a $100-150 difference — trivial for most businesses but worth noting for bootstrapped projects. Use Domain Cost Calculator for exact current pricing at major registrars. ### [[Memorability]] and User Perception This is where the extensions diverge significantly based on audience. **Developer audience (technical users):** - .io: Immediately recognized, positive association - .dev: Growing recognition, explicitly developer-positioned - .app: Recognized, associated with polished products **Non-technical audience:** - .io: Unfamiliar, some confusion - .dev: Almost unknown outside tech - .app: Some recognition (iOS/Android "apps" are culturally embedded) If your product has any non-technical user base — executives, marketers, operations teams — .app has the clearest cross-audience comprehension. "It's an app" translates; "it's a dev tool" or "it's io" does not. ### Trust Signals TLD Trust Signal analysis by audience: **Investors/VCs:** All three are well-understood in the venture community. No meaningful difference. .io has slight familiarity advantage from longer tenure. **Enterprise procurement:** .app > .io > .dev. Enterprise IT departments occasionally flag unfamiliar extensions. .app's Google backing and HTTPS enforcement help. .dev's name may trigger policies filtering "development" URLs (some IT policies block non-production-sounding domains — irrational but real). **Consumer users:** .app > .io > .dev. Consumers have the most positive associations with .app due to mobile app cultural context. ### TLD SEO Impact Google has confirmed all three extensions are treated identically in search ranking algorithms. The TLD SEO Impact from extension choice is effectively zero. The indirect SEO effects are: - HTTPS enforcement on .app and .dev is table stakes for SEO anyway - Click-through rates from SERP results may vary by user familiarity with the extension - Brand recognition drives CTR more than extension recognition ## Real-World Usage Patterns ### Who Uses .io - **Linear** (linear.app formerly linear.io) — Project management - **Socket.io** (socket.io) — JavaScript library - **Itch.io** (itch.io) — Indie game marketplace - **Codepen.io** (codepen.io) — Frontend playground - **Cypress.io** (cypress.io) — Testing framework - **Bubble.io** (bubble.io) — No-code platform ### Who Uses .dev - **web.dev** — Google's developer learning platform - **flutter.dev** — Google's Flutter framework - **css.tricks** (formerly, now uses .com) — CSS resource - Countless open-source project documentation sites ### Who Uses .app - **Linear** (linear.app) — Project management (migrated from .io!) - **Framer** (framer.app) — Design tool - **Miro** (miro.com/app) — Note: uses subdirectory, not TLD - **Codeflow** (codeflow.app) — Developer environments - **Raycast** (raycast.com) — Note: uses .com; raycast.app redirects Linear's migration from linear.io to linear.app is instructive. They explicitly chose .app for the "cleaner positioning as an application rather than a developer tool" — even though their user base is technical. ## Decision Matrix Answer these questions in order: **1. Is your primary audience developers?** - Yes → .dev or .io - No → .app **2. For developer-primary products: Is it a framework, library, or open-source tool?** - Yes → .dev (community association is strong) - No → .io (more commercial connotation) **3. Can you accept mandatory HTTPS from day one?** - Yes → .app or .dev qualify - No → .io (only option without HTTPS requirement) **4. Is budget a significant factor?** - Yes → .dev (cheapest of the three) - No → Choose based on positioning **5. Do you need non-technical audience comprehension?** - Yes → .app - No → Any of the three ## The Migration Consideration Many companies start on .io and later move to .app or .com. The migration cost is real: - 301 redirects must be maintained indefinitely - WHOIS history and Domain Valuation don't transfer - Backlinks and SEO authority take months to transfer fully - Brand materials, business cards, investor decks all need updating Choose with the 5-year view in mind. If you'll want .app eventually, start there. ## Verdict **Choose .io if:** You're an established-style dev tool, you want the longest-standing tech credibility, or mandatory HTTPS is a constraint. **Choose .dev if:** You're explicitly building for developers (framework, library, SDK, API), pricing matters, and your brand name works without the "app" connotation. **Choose .app if:** You're building a user-facing application (even if technically sophisticated), you want the broadest audience comprehension, and you want Google registry stability. For the broader startup TLD context, see Best TLDs for Startups in 2026. For the complete decision framework applicable to any TLD choice, see TLD Decision Framework: A Step-by-Step Guide.