Learn: domains, TLDs and drop lists

Plain-English guides written for people who register, buy, defend or study domain names. Start with the lifecycle if you are new, or jump to a TLD.

Updated November 2026

Guides

In-depth explainers on expired and dropped domains, the domain lifecycle, zone files, DNS, security and domain investing.

How to Check If a Domain Name Is Really AvailableRegistrar search, RDAP, WHOIS and DNS answer different questions. Learn which check to trust, why NXDOMAIN is not proof, and the dig, whois and curl commands.
Choosing a TLD for Your Startup: A Decision FrameworkA decision framework for picking a domain extension: trust, email, SEO myths, HSTS-preloaded TLDs, renewal pricing traps, trademarks and buying .com later.
Nameservers, Delegation and DNS Providers ExplainedWhat nameservers are, how delegation, NS records, glue and DS work, registrar DNS vs third-party DNS, and how to switch nameservers safely without downtime.
Domain Name Glossary: Registry, DNS and Lifecycle TermsPlain-language domain glossary: A record, EPP status codes, grace and redemption periods, RDAP, UDRP, punycode, zone file and 80+ more terms in A-Z order.
Domain Investing: How It Works and What Can Go WrongHow domain investing works: where value comes from, how to acquire names, holding costs, trademark and UDRP risk, common scams and a hypothetical portfolio.
The Domain Lifecycle: From Registration to ReleaseThe domain lifecycle from registration to release: renewal grace up to 45 days, 30-day redemption, 5-day pending delete, ICANN's ERRP, and ccTLD differences.
Drop Catching and Domain Backorders: How They Work and What the Odds AreHow drop catching and backorders work: registrar backorders vs drop-catch services, the .com drop, EPP races, auctions, fees and why most catches fail.
Dropped vs Expired vs Deleted Domains: Terms ExplainedExpired, dropped, deleted, pending delete, on hold and suspended mean different things. A terminology table plus how zone-file diffing reads each state.
How to Evaluate an Expired Domain Before You Buy ItDue-diligence checklist for expired domains: archive history, backlinks, spam signs, blocklists, trademarks, handles, with a scoring table and worked example.
Expired Domains: What They Are and Where to Find ThemWhat an expired domain really is, where expired and dropped lists come from, a repeatable sourcing workflow, and what a list can and cannot tell you.
gTLD, ccTLD and New gTLD: How Top-Level Domains Are ClassifiedHow TLDs are classified: legacy gTLDs, sponsored, country codes, the 2012 new gTLD round, brand and geo TLDs, residency rules and generic-use ccTLDs.
How Many Domain Names Exist, and Why Every Count DiffersVerisign's DNIB reported 411.6 million registrations in Q3 2026. See why zone-file, registry and registrar counts differ and what gets double-counted.
IDN, Punycode (xn--) and Homograph AttacksHow internationalized domain names work: xn-- punycode with computed examples, IDNA versions, homograph attacks, browser display rules and detection.
Newly Registered Domains: Risk, Feeds and Blocking PolicyWhy newly registered domains carry elevated risk, how NRD feeds come from zone-file diffs, and how to set blocking policy without too many false positives.
How to Stop Your Domain From Expiring by AccidentWhy domains lapse by accident and how to stop it: auto-renew, multi-year terms, locks, renewal recovery costs, a quarterly checklist and expiry monitoring.
Typosquatting and Lookalike Domains: Detect, Monitor, Take DownTyposquatting and lookalike domains: the main typo classes with an example table, a brand monitoring workflow, takedown routes and defensive registration costs.
WHOIS vs RDAP: What Changed and How to Query Domain Registration DataWHOIS vs RDAP compared: port 43 text versus JSON over HTTPS, ICANN's January 2025 change, GDPR redaction, a real RDAP query, IANA bootstrap and rate limits.
DNS Zone Files and ICANN CZDS: What They Are and How to Get AccessWhat a TLD zone file contains, what ICANN CZDS is, how to request access, what the terms usually restrict, and what zone data cannot tell you about a domain.

TLD guides

One guide per extension: who runs it, how it is priced and used, its reputation, and who it suits.

.ai domains: how a Caribbean ccTLD became AI brandingHow .ai became the default for AI startups: Anguilla government ownership, the 2025 move to Identity Digital, pricing patterns, SEO treatment and caveats.
.app domains: a TLD that refuses plain HTTPThe .app TLD is run by Google's registry and preloaded for HTTPS in browsers. Operator, rules, audience, SEO treatment and who should (and should not) pick it.
.art: a portfolio address for creators.art is a creative-industry TLD run by UK Creative Ideas with CentralNic as back end. Registry facts, eligibility questions, pricing patterns and who uses it.
.baby: a niche parenting extension that changed hands.baby began with Johnson & Johnson in 2016 and is now run by XYZ.COM LLC. See who uses it, how a niche vertical TLD behaves and the trade-offs of buying one.
.biz domains: a business-only rule that is hard to enforceEverything about .biz: the 2001 launch, Neustar to GoDaddy Registry, the bona fide business-use rule, the STOP dispute policy, pricing, reputation and fit.
.blog and Automattic: what Knock Knock WHOIS There runs.blog is run by Automattic through Knock Knock WHOIS There, LLC. Read how it launched in 2016, how it relates to WordPress.com and when it makes sense.
.bond: a finance-sounding TLD that is open to everyone and heavily abusedThe .bond TLD explained: a former university brand extension relaunched by ShortDot in 2019, open to all, with a heavy phishing record and advice for owners.
.cfd: contracts for difference, clothing and fashion design, or just a cheap TLD?What .cfd stands for, why a trading term became a general TLD, who operates it, how it ranks in spam data, and what to check before you register one.
.cloud: a registry run by a hosting company.cloud is an open TLD operated by Aruba PEC, a subsidiary of the Italian hosting group. Registry facts, typical SaaS and hosting uses, pricing and trust issues.
.club: the community TLD that launched with a bang.club opened to the public in May 2014 and drew tens of thousands of names on day one. Learn who runs it, who uses it, how it is priced and what to check first.
.co: Colombia's code, sold as "company" and "community".co is Colombia's ccTLD, opened worldwide in 2010 as a short alternative to .com. Learn the 2025 operator change, rules, SEO treatment, pricing and trade-offs.
.com domains: why the biggest namespace stays the defaultA fact-based guide to .com: Verisign as operator, 1985 origins, the enormous aftermarket, how drops work and how wholesale price caps shape renewals.
.dev: the developer TLD with HTTPS built in.dev is a Google Registry TLD with HTTPS enforced through HSTS preload. Learn the operator, launch, who uses it, pricing patterns, SEO treatment and caveats.
.icu: from a hospital acronym to a budget TLD with a "see you" pitchGuide to the .icu TLD: how a hosting company's string became a ShortDot budget extension, what it means, how it is used, how filters see it, and pricing.
.info domains: the 2001 experiment that opened the namespaceThe .info TLD explained: the first unrestricted new gTLD of 2001, run by Afilias and now Identity Digital, its spam-heavy reputation, pricing and best uses.
.io: a startup favorite with a geopolitical footnoteThe .io ccTLD belongs to the British Indian Ocean Territory yet became a startup staple. Operator, Chagos treaty uncertainty, pricing and SEO treatment.
.live: when the page itself is the event.live is an open TLD for streaming, events and broadcasts, run by Identity Digital affiliates since 2015. Registry facts, uses, pricing patterns and cautions.
.me: a Montenegrin ccTLD built for personal sites.me is Montenegro's ccTLD, sold worldwide for personal sites and "me" wordplay. Operator, 2008 launch, rules, SEO treatment, pricing and caveats explained.
.net domains: the infrastructure TLD that became everyone's plan BGuide to .net: its infrastructure and ISP heritage, Verisign operation, why it became the usual second choice to .com, and how it prices and performs.
.online: the broad Radix flagship and its reputation problem.online is Radix's broad open gTLD, delegated in 2015. Learn its operator history, who uses it, how abuse rankings affect it and how renewals tend to price.
.org domains: a nonprofit label with no nonprofit requirementWhat .org really means: open registration, the Public Interest Registry, the 2019 price-cap removal and the blocked Ethos Capital sale, and pricing.
.pro domains: the credentialed TLD that quietly opened upHow .pro went from a credential-checked domain for lawyers, doctors and accountants to open registration, via RegistryPro, Afilias and Identity Digital.
.sbs: how an Australian broadcaster's brand TLD became an open extensionThe .sbs TLD began as an Australian broadcaster's brand extension and is now an open ShortDot gTLD. Read the history, rules, spam rankings and cautions.
.shop domains: the ecommerce extension that launched in 2016.shop is an open gTLD run by GMO Registry and delegated in 2016. See what the extension signals for ecommerce, how pricing behaves and what to weigh first.
.site: the catch-all extension for projects with no category.site is an open Radix gTLD delegated in 2015. Learn what it suits, how it compares with other generic new TLDs, and what to know about price and reputation.
.store or .shop? How the two retail extensions really differ.store is a Radix-run retail gTLD delegated in 2016. Compare it with .shop on operator, history, reputation and pricing to decide which retail suffix to buy.
.tech: the extension that says what you build.tech is a generic TLD run by Radix since 2015. See who uses it, how renewal pricing behaves, how it reads to founders, and what to check before you buy.
.top: a very large budget TLD with a reputation problem to manageWho operates .top, how it grew to millions of names, why it tops spam and phishing tables, and what a legitimate site should weigh before registering one.
.vip: a status word that found its biggest market abroad.vip is an open TLD that sold heavily in China after its 2016 launch. See the registry history, who uses it, pricing patterns and the risks worth checking.
.wiki: a home for knowledge bases, docs and fan wikis.wiki is an open TLD from 2014, now managed by GoDaddy Registry and unrelated to Wikimedia. Registry history, uses for docs and fan wikis, pricing and risks.
.xyz: the generic extension that grew by being the cheap alternativeWhat the .xyz TLD is, who runs it, why Alphabet uses abc.xyz, how its low prices shaped its reputation, and when it is a sensible choice for a project.
.zone: a flexible word for places, areas and communities.zone is a generic TLD from Identity Digital's portfolio. Registry details, typical uses for communities and side projects, plus price and trust notes.

Comparisons

Fair side-by-side comparisons of tools and extensions.

Budget New gTLDs Compared: .xyz, .top, .online, .site, .shop, .storeCompare budget new gTLDs .xyz, .top, .online, .site, .shop and .store: operators, promo vs renewal pricing, abuse reputation and a decision matrix.
.com vs .io vs .ai vs .app for StartupsChoosing between .com, .io, .ai and .app for a startup: who runs each, the rules and risks, HSTS on .app, .ai two-year terms, and the .io treaty uncertainty.
.com vs .net vs .org: The Legacy gTLD Trio Explained.com vs .net vs .org: who runs each, how they started, who uses them, how Verisign's price caps work, .org's nonprofit operator and which to register first.
.dev vs .app: Two Google TLDs, Two Audiences.dev vs .app compared: same Google registry, same HSTS preload, different audiences. Launch dates, use cases, HTTPS and mixed content, email and naming advice.
Expired and Dropped Domain Tools ComparedCompare expired domain tools: ExpiredDomains.net, DomCop, SpamZilla, Instant Domain Search and auction houses, by data source, metrics, price model and use.
ExpiredDomains.net Alternatives, Chosen by Use CaseLooking beyond ExpiredDomains.net? See which alternatives fit SEO buying, branding, security research and domain investing, and when staying put makes sense.

Prefer Vietnamese? See the Vietnamese guides.