What is Sui (SUI)?

Sui is a blockchain for smart contracts and apps. Its coin is SUI. It grew out of Diem, a payments project at Meta that was abandoned, and uses a programming language from that project called Move.

Where it came from

Sui's main network went live in May 2023. It was built by Mysten Labs, which raised $300 million in September 2022 in a round led by FTX Ventures. Sui was the second blockchain, after Aptos, to come out of Diem's Move language.

How it works

• Proof of stake. Validators stake SUI, and holders delegate SUI to the validators they choose (Lesson 8). Changes to stake take effect at the start of each epoch, which lasts 24 hours.
• Move. Smart contracts (Lesson 7) are written in Move, the language that came out of Diem.
• Storage fund. Storing data on Sui costs a fee that goes into a fund. The fund's returns pay validators for keeping that data. If you delete data, you get part of the fee back.

Supply

• The total is capped at 10 billion SUI.
• Not all of it is in circulation. The rest is released on set schedules over time.
• SUI pays transaction fees and storage fees, is staked to secure the network, and is used to vote on upgrades.

What people use it for

People use apps built on Sui, such as exchanges, stake SUI and use it to pay fees.

Risks to know

• Validators can freeze funds. On 22 May 2025, about $223 million was drained from Cetus, an exchange on Sui. Validators blocked about $162 million in the attacker's addresses, and a holder vote later approved returning it. That protected users, but it shows that a small group can stop transactions on Sui.
• Scheduled releases. Tokens still to be released add to the supply over time.
• App risk. Lesson 45 explains how bugs in DeFi apps lose money, as Cetus did.
• Price swings. SUI can fall far and fast, like other coins.

Learn more

Lesson 7 covers smart contracts, Lesson 41 introduces DeFi, and Lesson 45 covers the risks of DeFi.