What one USDC actually is

A dollar that lives on a blockchain

A stablecoin is a token on a public blockchain that is designed to keep a fixed price against a currency. USDC, issued by the US company Circle, and USDT, issued by Tether, are the two largest, and both aim at one US dollar.

The problem they solve is simple. Crypto markets run all day, every day, on blockchains. Bank transfers do not. They stop at weekends, take a day or more to cross borders, and a crypto firm often struggled to keep a bank account at all. A token that behaves like a dollar but moves like any other crypto asset lets a trader, a company or an app hold dollars and send them in minutes, at any hour, to anyone with a wallet. That is why stablecoins became the settlement currency of crypto trading first, and now show up in payments and treasury management as well.

The market is large and concentrated. About 312 bn USD of stablecoins existed on 4 September 2026, according to DefiLlama, and USDT and USDC together made up about 83% of the dollar-pegged part. So when people say "stablecoin", they usually mean one of these two, and USDC is the easier one to study because Circle publishes a lot about how it works.

The claim printed on every USDC is short: one USDC equals one US dollar. That sentence hides three separate things. Each can hold while another fails, and most mistakes about stablecoins come from mixing them up.

Layer one: the token

The first layer is the token itself. USDC on Ethereum is a smart contract, a small program on the blockchain that keeps a list of addresses and how many tokens each one holds. When you "send" USDC, the program subtracts from one balance and adds to another. Nothing else happens.

The contract has no link to a bank and no idea what a dollar is. If USDC traded at 60 cents tomorrow, the contract would behave exactly as it does today. Only Circle can create new tokens or destroy them. Minting adds new tokens to the total, and burning removes them. Anyone can read the total supply on-chain at any moment.

That total is useful, but it is a count of what Circle owes, not proof that anything backs it. The blockchain shows the liabilities. It cannot show the assets, because the assets sit in banks and funds off-chain.

Layer two: the issuer's promise

The second layer is legal: someone has promised to swap the token for a dollar. For USDC that someone is Circle, and the promise has conditions.

Redemption is handing a stablecoin back to the issuer and receiving dollars in a bank account. Circle Mint is Circle's desk for business customers, and the only place USDC can be redeemed. A company opens an account, passes identity checks (known as KYC, "know your customer"), signs an agreement, and can then send dollars to get new USDC or send USDC back to get dollars, one for one. Tether runs the same kind of desk for USDT. Kaiko, a market-data firm, reported in April 2026 that direct USDT redemption needs a verified account and about 100,000 USD.

Most holders never touch these desks. If you bought USDC on an exchange or received it as a payment, you have no account at Circle Mint. Your way out is to sell the token to someone else at whatever the market pays, usually on an exchange. That is the most important fact in this chapter, and it surprises many people who have held stablecoins for years.

A stablecoin is also not a bank deposit. No deposit insurance covers it. If an issuer failed, holders would be creditors of a private company, and how well they came out would depend on how the reserve was legally separated from the company's other assets. Since 2025 the US has a dedicated stablecoin law. The GENIUS Act, the federal stablecoin law signed on 18 July 2025, defines a payment stablecoin by exactly this promise: the issuer must redeem it for a fixed amount of money.

Layer three: the reserve

The third layer is the pile of assets that stands behind the promise. A reserve is the cash and short-term government debt an issuer holds so it can pay out when tokens come back.

Circle keeps most of the USDC reserve in the Circle Reserve Fund, a money-market fund managed by BlackRock that holds short US Treasury bills and repo (overnight loans secured by Treasuries). An attestation by Deloitte dated 6 November 2025 put about 87% of the reserve in that fund and the rest in cash at banks. An attestation is an accountant's check, on one stated date, that the issuer's report of its assets is accurate. It is a snapshot, not a full audit.

Those Treasury bills earn interest, and USDC holders receive none of it. The GENIUS Act bars issuers of payment stablecoins from paying interest to holders, so the income stays with the issuer and its partners. That is the whole business model of a fiat-backed stablecoin, and How stablecoin issuers make money follows the money in detail.

How minting and redemption keep the price near 1 USD

The reserve does not set the price by itself. The price on an exchange is whatever buyers and sellers agree on, and it moves all day. What pulls it back to 1 USD is a trade that pays whenever the price drifts.

The peg is the target price, here 1 USD. Arbitrage is buying something where it is cheap and selling it where it is dear, and stablecoins rely on it in both directions.

1. USDC falls to 0.995 USD on an exchange. A Circle Mint customer buys it there, hands it to Circle, and receives 1.00 USD per token. The customer keeps half a cent per token, and all that buying pushes the exchange price back up.
2. USDC rises to 1.005 USD. The same customer sends dollars to Circle, receives new USDC at 1.00 USD, and sells it on the exchange. The selling pushes the price back down.

As long as both doors stay open, cheap and fast, the price cannot wander far from 1 USD. The reserve matters because it lets Circle pay on the first trade. But a reserve that nobody can reach does not hold the price.

March 2023 showed what happens when a door closes. On Friday 10 March, US regulators closed Silicon Valley Bank, where Circle held 3.3 bn USD of USDC reserves, about 8% of the total. Banks were shut for the weekend, so redemptions could not settle. The rest of the reserve was still there, mostly in Treasury bills. Even so, USDC traded down to about 0.87 USD on Saturday 11 March. On Sunday the US authorities said all SVB deposits would be protected. The banks opened on Monday, the trade started working again, and USDC was back at 1 USD within days.

The next chapter walks through this weekend and four other crises that shaped the market.

Why this matters

For a holder, the three layers answer three different fears. "Is the contract safe?" is a question about layer one. "Will anyone pay me a dollar?" is layer two, and for most holders the answer is "only the market will". "Do the assets exist?" is layer three, answered by attestations and, for some issuers, not answered as well as it should be.

For a builder, the layers explain design choices. An app that holds customer funds in USDC takes on Circle's promise and Circle's banks, and gives its users no deposit insurance. An exchange that lists a stablecoin cares most about how fast arbitrage traders can mint and redeem, because that decides how tightly the price holds when markets get rough.

For the market, the layers explain why two tokens dominate. Anyone can write a token contract in a day. Building a redemption desk that banks will serve, reserves that auditors will sign, and enough trading depth that the arbitrage stays cheap takes years. Tether shows the uncomfortable side of this: it paid penalties to the New York Attorney General (18.5 mn USD) and the CFTC (41 mn USD) in 2021 over statements about its reserves, and USDT still holds the largest share of the market. Liquidity and acceptance have mattered more to its price than transparency. Transparency matters when things break.

How this course is organised

The course follows one arc: how stablecoins started, how they work, where the market is today, and what comes next. Each chapter stands alone, but they build on each other in this order.

Foundations (the past):

• What one USDC actually is: this chapter.
• A short history of stablecoins in five crises: how each failure shaped the designs that survived.

How it works:

• How a peg holds: five designs: fiat-backed, crypto-backed, synthetic, algorithmic and bank-issued tokens.
• Under the hood: reserves, minting, redemption and freezes: the contracts and the powers issuers keep.
• Which chains stablecoins live on, and who distributes them: Ethereum, Tron, Solana and the firms that hand tokens to users.
• The rules: GENIUS Act, MiCA and the global map: how the US, the EU and others license issuers.

The market today:

• Where stablecoins stand in September 2026: the dated numbers in one place.
• How stablecoin issuers make money: interest on reserves, and who shares it.
• Where stablecoins are actually used: trading, cross-border payments and savings.
• Who's who in stablecoins: issuers, distributors and infrastructure.

What's next:

• What works, what doesn't, and 2027 to 2030: scenarios and signals.
• How to analyze any stablecoin in 30 minutes: a checklist that uses everything above.

What to watch next

• Final US rules under the GENIUS Act: regulators had published proposals but no final rules by September 2026, and the law takes effect by 18 January 2027 at the latest. The final text will fix who may issue, what reserves may hold and how fast redemptions must be paid.
• Wider redemption access: most holders cannot redeem with the issuer today. Any issuer that opens redemption to ordinary users, or shortens settlement to weekends, strengthens its peg for everyone.
• Tokenized bank deposits: JPMorgan's deposit token JPMD went live on Base, a public blockchain, in November 2025. If banks bring deposits on-chain with deposit-style protection, stablecoins lose part of their reason to exist for large companies.
• Reserve reporting: watch whether the largest issuers move from monthly attestations to full audits of their reserves. That is the gap between layer three as promised and layer three as proven.