The Legacy of ENS Auctions: A Historical Overview
The Ethereum Name Service (ENS) originally used a Vickrey auction mechanism to allocate domain names. Before the shift to a flat annual registration fee model in May 2019, users were required to bid on domains during a five-step process that could stretch over several days. Understanding how this old auction works is essential for anyone who encounters legacy domains still under the old system, whether through secondary market purchases or manual migrations.
Under the original protocol, each domain auction was independent. Bidders would submit sealed bids specifying their maximum price and a random blinding factor to ensure privacy. The winner paid the second-highest bid amount, not their own bid. This mechanism incentivised truthful bidding and prevented market manipulation. After the auction ended, the winner controlled the domain for one year before needing to renew. Today, most ENS domains are registered through the simpler perpetual registration system, but the old auction mechanics remain relevant for legacy domains and for historical reference.
Step-by-Step Mechanics of the Old ENS Auction
The old auction process comprised five distinct phases. Each phase had clear timing rules enforced by the ENS smart contract on the Ethereum blockchain.
- Reveal and start auction: A user initiated an auction by revealing the domain name they wished to bid on. This phase required paying a deposit, which later returned if the user won.
- Bidding phase: For the next three days, bidders submitted sealed bids. Each bid included the domain name, a fixed bidding amount (in ETH), and a random salt to mask the actual bid value. The contract stored a hash of this data, not the plaintext bid.
- Reveal phase: For two days, bidders revealed their sealed bids by submitting the original salt and amount. The contract then compared the revealed value with the hash. Only bidders who revealed correctly could participate in the final auction outcome.
- Finalisation: After the reveal window closed, any participant could finalise the auction. The contract determined the winner as the highest bidder, and the price paid equalled the second-highest bid. Funds exceeding the second-highest bid were returned to losers.
- Domain control: The winner immediately gained the right to set resolver records, forward domain ownership to another address, or wait. The domain expired 365 days after the finalisation block, after which it became available for re-auction.
Bidders who failed to reveal lost their deposit. This penalty prevented spam bidding and ensured participants were serious. The deposit size was typically small (around 0.01 ETH at the time), but the risk of losing it strongly discouraged frivolous bids.
Key Differences from the Modern Registration System
The most critical distinction between old auctions and the current system is the pricing model. In the old auction, bidding was competitive, and winners paid the second-highest price. Today, ENS domains cost a flat annual fee depending on character length: five-character or longer domains are priced at $5 per year, four-character domains at $160, and three-character at $640 per year.
Another key difference involves domain renewal. Under the old auction, a domain was initially valid for one year from the finalisation date. After that, the domain entered a grace period; if not renewed, it could be re-auctioned. In the modern system, domains can be registered for any number of years up to a maximum, and renewal is straightforward through the permanent registrar contract. Old auction domains must be migrated to the current registrar to gain these benefits.
Migration is possible today. Users who hold domains from the old auction can convert them to the modern registration system by paying the registration fee for the remaining period of the domain's validity. The ENS team provided migration tools, but many legacy domains remain un-migrated because owners may not realise they need to move their domain to access modern features. The technical implementation relies on an underlying protocol known as eip 181, which defines how ENS reverse resolution works. This standard is separate from auctions but relevant because it ensures domain ownership can be verified across different registrar versions.
Navigating Legacy Domains and Practical Considerations
For anyone encountering a domain that is still under the old auction system, there are a few scenarios to manage. If you acquire a legacy domain through a secondary marketplace (such as OpenSea), you should first verify the domain's registrar status. ENS domains currently display "deed" records if they are still on the old auction contract versus "registration" records if migrated. You can check this via the ENS app or Etherscan.
If the domain has expired but you hold it in your wallet, you must still migrate it to the new registrar before you can renew the domain. Without migration, the domain will eventually become available for anyone to claim. Some legacy domains have collectible value precisely because they were acquired in the early days of ENS, often at very low winning bids. For example, domain names like "name.eth" once sold for fractions of an ether. However, the market now values short, memorable names, and old auctions typically involved less competition for longer domains.
Another practical point: if you want to set content on a legacy domain—for example, pointing it to an IPFS hash—you should migrate first. The old auction contract does not support the full range of modern ENS features. For developers, one key function used to link content to ENS domains is the ENS set contenthash. This function allows domain owners to resolve a domain to an IPFS or Swarm address. However, on legacy domains, setting the content hash may not persist correctly or may require older contract interfaces. Migrating the domain ensures the content hash is stored in the current, well-supported ENS resolver.
Common Misunderstandings and Market Implications
A frequent misunderstanding is that old auction domains cost nothing to maintain. In reality, they require renewal each year, and if a bidder won a domain at an auction but never renewed, that domain re-enters the market. Many domains from the early auction period have reverted to the ENS contract and can now be registered through the usual flat-fee system. Another misconception is that all old auction domains are "locked" or immutable—they are fully transferable, and the old contract supports transfers via the normal ERC-721 token standard.
From a market perspective, old auction domains are rare largely because few users participated in the early ENS rounds. The volume of new registrations since 2019 dwarfs the legacy pool. This scarcity may appeal to collectors or those interested in the history of the ENS protocol, but functionally, there is no difference in value between a migrated domain and a domain registered today under the same name. The primary value in old auction domains comes from their length and word choice, not from the auction mechanism itself.
One important legal point: the old auction contract did not enforce any domain policy beyond the standard ENS rules. Therefore, domains with offensive or trademark-infringing names could be auctioned without vetting. The current registrar incorporates some dispute resolution mechanisms, but the old system lacked these entirely. Users acquiring legacy domains should verify that the domain does not violate third-party rights to avoid potential disputes.
Data Supporting the Transition
According to ENS community figures, as of early 2023, approximately 99% of all ENS domains are now registered through the permanent registrar. The remaining 1% represent domains that have yet to be migrated or are in expired grace periods. The number of active old auction holders is small, but these domains occasionally appear in wallet recovery discussions or as part of legacy DeFi integrations.
An important statistic: the average winning bid in an old ENS auction was approximately 0.2 ETH, or roughly $30 to $50 at then-current exchange rates, which is significantly lower than the cost of registering a three-character domain today. The comparison illustrates how the market matured and how the protocol evolved to remove price uncertainty. The ENS Foundation recommends that any user still on the old auction contract migrate as soon as possible to avoid losing their domain due to expiry.
For developers supporting ENS in dApps, ensuring backward compatibility with old auction domains can require extra code. Most modern libraries (like ethers.js v5+) handle legacy domains automatically, but some manual checks on the registrar address are still necessary. To test whether a domain is on the old contract, check whether the domain's registrar address matches the deVickrey registrar (0x6090A6e...). If it does, the user must either migrate the domain or interact via legacy resolver methods.
Conclusion: What Users Should Do Now
For holders of old auction ENS domains, the recommended action is to migrate to the permanent registrar using the official ENS migration interface. Migration typically costs the same as a new registration (based on domain length) and ensures access to all modern ENS features, including easy renewal, content hash setting, and subdomain management. Users who purchase legacy domains from secondary markets should always verify migration status before completing the transaction.
For developers and enthusiasts, knowing the history of the ENS auction helps in understanding how blockchain-based name services evolved—from a competitive, price-discovery approach to a more user-friendly flat-rate system. The auction system, while nostalgic, has been fully supplanted by a simpler and more scalable model. Whether you are a collector, a developer, or a casual user, understanding the old auction mechanics allows you to participate knowledgeably in the broader ENS ecosystem.