Bulk Domain Checker for .com, .ai, .io, and .co TLDs (2026)

Quick answer The four TLDs that cover most startup needs are .com (default, cheapest, most trust), .io (developer-focused, ~$40-60/yr), .ai (AI-focused, ~$80-200/yr), and .co (general purpose, ~$25/yr). A bulk checker that supports all four in one query lets you brainstorm once and check availability everywhere at the same time. Bulk Domain Checker Pro covers all four and more in Chrome.

Check all four TLDs in one query

.com, .ai, .io, .co - plus 50+ more. Chrome extension, free to install.

Add to Chrome - Free

Why these four specifically

Thousands of TLDs exist in the domain name system, but for most new tech startups, the decision reduces to four. Each carries a different signal, different cost, and different set of tradeoffs.

.com

Price: ~$10-12/year at most registrars

Signal: Default, established, trustworthy

Who uses it: Almost everyone. Absence of a .com is usually noticeable.

Availability: Increasingly hard for short, pronounceable names. Three-letter .coms are essentially all taken on the aftermarket. Two-word combinations remain available.

Verdict: The default. If you can get a reasonable .com, take it. For consumer products where name recognition matters most, prioritize .com over alternatives.

.io

Price: ~$40-60/year, depends on registrar and premium status

Signal: Tech-forward, dev-oriented, infrastructure/SaaS startup

Who uses it: Developer tools, APIs, infrastructure companies, many YC startups.

Availability: Better than .com but narrowing. Short, pronounceable .io domains are still findable but increasingly expensive as "premium" pricing.

Verdict: Strong choice for dev tools and B2B SaaS. Overkill for a consumer product. The 4x price premium over .com is justified only if the audience actively appreciates the .io signal.

.ai

Price: ~$80-200/year, with significant registrar variation

Signal: AI product. Unambiguously.

Who uses it: AI startups, ML companies, anything with machine learning as a core feature.

Availability: Tight. The AI boom of 2022-2026 drove massive demand. Good names are often taken or premium-priced. Some premium .ai domains hit $10k+ in the aftermarket.

Verdict: Use it if you genuinely make an AI product. The signal is strong and category-defining. Avoid if AI is just a marketing hook - the audience of sophisticated AI buyers is learning to discount .ai-branded products that aren't actually AI-first.

.co

Price: ~$25-35/year

Signal: Short for "company" or "corp" - general purpose, often seen as a .com alternative

Who uses it: Startups, agencies, consumer brands where .com is taken.

Availability: Moderate. Better than .com, worse than newer TLDs. Popularity has grown since Colombia's registry opened .co globally.

Verdict: Underrated. A short, clean name on .co reads well and is often available when .com is taken. Less specific signal than .io or .ai, which is a feature if your product doesn't fit those categories.

Which TLD fits which startup

Startup type	Primary TLD	Backup TLD
Consumer app / B2C	.com	.co
AI / ML product	.ai	.com
Developer tool / API	.io	.com or .dev
B2B SaaS (non-dev)	.com	.co or .io
Infrastructure / open source	.io	.com
Agency / services firm	.com	.co
Newsletter / media	.com	.co

Check your name across all four

Pick .com, .ai, .io, .co (or add more) and check your whole name list in one query.

Add to Chrome - Free

Bulk checking across these TLDs

The reason a bulk checker matters for TLD research: if you have 30 name candidates and want to know availability across 4 TLDs, that's 120 individual lookups. Doing them one by one at a registrar takes 30-45 minutes. Bulk checking takes under a minute.

Workflow in Bulk Domain Checker Pro

Open the extension popup in Chrome.
Paste your 30 root names (one per line).
In the TLD filter, tick .com, .ai, .io, .co. Save as a group called "Startup Four" for reuse.
Click Check.
Results populate as a grid: rows are names, columns are TLDs, cells are green (available) or red (taken).
Export to CSV if you want to filter in Sheets.

Registrar price differences for these TLDs

Once you've found available domains, price comparison matters - especially for .io and .ai where the difference between registrars can be $30+/year.

Generally cheapest for these four TLDs (as of April 2026):

.com: Porkbun, Cloudflare Registrar (at-cost), Namecheap. Most registrars within $2 of each other.
.io: Porkbun and Namecheap usually competitive. Premium pricing is registry-driven and applies equally everywhere.
.ai: Porkbun and Namecheap again. Watch for first-year vs renewal-year pricing - some registrars discount the first year heavily.
.co: Namecheap and Porkbun typically. GoDaddy often most expensive.

Prices change. Always compare at the moment of purchase via each registrar's own search.

Should you register all four?

Short answer: no, usually.

For most pre-launch startups, register your primary TLD and maybe one defensive variant (e.g., get .com if that's your primary, add .co as defensive; or get .io and add .com if available). Registering all four as a pre-seed company is $150+/year on domain fees for no near-term benefit.

Once you're revenue-positive and have real brand traffic, defensive registrations become more worthwhile. A competitor grabbing your-brand.io when you're on .com is annoying and occasionally damaging. At that point, buy the major TLD variants and redirect them.

Common TLD mistakes

Picking .ai when you're not an AI product. The signal is getting sharper. "AI" in your TLD should correspond to actual AI in your product, or the audience starts to discount you.

Picking exotic TLDs to save money. .xyz, .site, .online, .top - prices are low ($1-5 for the first year) because adoption is weak. Users type .com by default; you'll lose traffic to the .com squatter. Exceptions exist (specific niche TLDs with real usage) but "cheap" is a bad reason.

Not checking all four at once. You register a .io, then three months later you want to also buy the .com and it's gone. Check all four upfront, even if you only register one.

Buying a premium domain for a pre-revenue startup. $200 to register a .ai domain is tolerable for established companies. For pre-seed, it's often a sign you're optimizing the wrong thing. Pick an affordable name, launch, and worry about the premium upgrade later.

Bulk Domain Checker for .com, .ai, .io, and .co TLDs