Assuming that you are referring to the Sui name service (SNS), which is a blockchain-based domain name service for decentralized applications, there are several competitors in the market offering similar services, including:
Ethereum Name Service (ENS): ENS is a similar service to SNS, but it is built on the Ethereum blockchain. It provides a decentralized domain name system for Ethereum-based decentralized applications.
Unstoppable Domains: Unstoppable Domains is another blockchain-based domain name service that offers decentralized domain name registration and resolution.
Handshake: Handshake is a decentralized, permissionless naming protocol that allows users to register and own top-level domains on a blockchain.
Namecoin: Namecoin is a decentralized naming system that is built on top of the Bitcoin blockchain.
These are some of the main competitors of SNS in the blockchain-based domain name service market. However, each of these services has its own unique features, advantages, and limitations, and the choice of which service to use ultimately depends on the specific needs and preferences of the user.