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Developer Documentation Glossary

The glossary provides a list of definitions for terms, acronyms, and phrases used in the Unstoppable Domains developer documentation to help its members understand common terminology.


The process of permanently destroying and clearing all the associated metadata and records of a domain, so it is no longer available for purchase or re-minting.


An interoperability protocol that allows tokens and arbitrary data to be transferred from one blockchain to another.


Crypto Name Service (CNS) is the name service handling .crypto domains on the Ethereum mainnet. It is depreciated as new domains are minted on UNS, which supports various domain endings besides .crypto.


Decentralized Application (DApp), also known as Decentralized Website (D-Website), is an application or website that exist and run on a blockchain or peer-to-peer network of computers instead of a single computer and is outside the purview and control of a single authority. They are usually powered by smart contracts.

Domain Ending

Also known as TLD or domain extension, it is the last segment of a domain name or the part that follows immediately after the dot (.) symbol, i.e., .crypto, .nft, .x.

Domain Resolution

The process of retrieving the records associated with an NFT domain, i.e., cryptocurrency addresses, chat IDs, and IPFS hashes for decentralized websites.


A fee or pricing value paid by a user to successfully conduct a transaction or execute a smart contract on the blockchain. This fee depends upon the transaction’s complexity and the current demand on the network.

Humanity Check

A feature provided by Unstoppable Domains which allows an application to anonymously verify their users' personal information using their NFT domains without revealing their identity.


InterPlanetary File System (IPFS) is a protocol and peer-to-peer network for storing and accessing files, websites, applications, and data in a distributed file system.


Layer 1 (L1) is the blockchain platform itself, also referred to as the base layer, mainchain, or mainnet, i.e., Bitcoin, Ethereum, Cardano, Litecoin, Solana, Polkadot.


Layer 2 (L2) is a secondary framework or protocol built on top of an existing Layer 1 blockchain. They are commonly used to improve scalability, privacy, and cross-chain communication. Unlike sidechains, which use their consensus mechanisms, Layer 2 protocols are secured by their underlying blockchain, i.e., Lightning Network, Optimism, Arbitrum.


This is the main blockchain protocol that is fully developed and deployed, meaning that cryptocurrency transactions are being broadcasted, verified, and recorded here.


A collection of data provides information about one or more aspects of another data, but not the content itself. It is used to summarize basic information about data which can make tracking and working with specific data easier, i.e., social media profiles of a person.


The process of validating information, such as domain ownership, and registering that onto the blockchain.

Name Service

A bundle of smart contracts hosted on the blockchain responsible for defining domain ownership rules, storing domain records and metadata, minting, resolving, and burning domains.


A one-way algorithm that converts a domain name like example.crypto into an ERC-721 token Id so smart contracts can understand it.

NFT Domains

The domain names minted on the blockchain which allow people to govern their data, set their Web3 username, take control of their digital worlds, and harness the power of the internet.


A service that supplies smart contracts with data from the outside world (such as real-world data from weather to stocks). Smart contracts cannot access off-chain data, so they rely on oracles to retrieve, verify, and provide external information, i.e., Chainlink and Band Protocol.


A user authorized by Unstoppable Domains to sell domains to users in their applications.


The data associated with an NFT domain, i.e., cryptocurrency addresses, chat IDs, and IPFS hashes for decentralized websites. It is stored as a key-value dictionary by the domain on the blockchain.


The naming service smart contract manages domain ownership, minting domains and subdomains, storing domain metadata, and burning domains. The registry also stores and manages domain records in the Unstoppable Name Service (UNS).


The Crypto Name Service (CNS) smart contract that is responsible for storing, updating, and resolving domain records.

Reverse Resolution

A feature that enables applications that integrate with Unstoppable Domains to show domain names where they would typically only show addresses.

Smart Contract

A smart contract is a contract whose terms are expressed as a computer program with logic and state persisted on the blockchain. Smart contracts can automatically carry out their terms and conditions with total transparency and no counterparty risk, allowing transactions to be made without an intermediary figure and trust between the parties involved.


A software environment that mimics a mainnet blockchain. It is used to test network upgrades and smart contracts before deploying them to the mainnet.


Short for Unstoppable Domains.


Unstoppable Name Service (UNS) is the name service handling the minting and management of NFT domains on the Ethereum (L1) and Polygon (L2) blockchains.


Zilliqa Name Service (ZNS) is the name service handling .zil domains on the Zilliqa mainnet.