Stablecoins Explained: What They Are and How USDT, USDC, and DAI Differ

A stablecoin is a cryptocurrency designed to hold a steady value against a reference currency — almost always the U.S. dollar. One token is meant to equal one dollar, at all times. The design works only if there is something credible behind that one-dollar promise, and that backing is where stablecoins genuinely differ from one another.

The scale is what makes the question matter. As of October 2026, Tether's USDT has roughly $184 billion in circulation, and Circle's USDC has roughly $73 billion — two private dollar tokens moving tens of billions between traders, businesses, and savers every day. They look interchangeable on an exchange screen. They are not. Understanding what sits behind each peg is the whole subject of this post.

The One Idea Behind Every Stablecoin

Strip away the branding and every stablecoin runs on the same mechanism: confidence in redemption. A token trades at $1 because holders believe they can always get $1 back — by redeeming with the issuer, or by selling to someone else who believes the same thing. Redemption is the pressure valve. When redemptions work smoothly, the peg holds. When they jam, the price slips, and if the reserves behind the token are insufficient, the slip becomes a collapse.

So the useful question is never "which stablecoin is best." It is "what is behind this particular dollar promise, who checked it, and on what terms can I get my dollar back." Everything below is a way to answer those three questions.

Three Designs, Three Kinds of Trust

Stablecoins fall into three backing models. The categories matter more than any single coin's marketing.

1. Fiat-collateralized: a company holds the dollars (USDT, USDC)

The simplest design. An issuer takes your dollars, issues one token per dollar, and holds the dollars (or dollar-like assets) in reserve. Redeem the token and the issuer hands the dollars back and destroys the token.

USDT is the largest, with about $183–184 billion in circulation in October 2026. Tether reports its reserves quarterly through attestations prepared by the accounting firm BDO. Its Q2 2026 attestation, covering June 30, 2026 and released July 31, 2026, showed $187.75 billion in assets against $183.64 billion in liabilities — a cushion of about $4.11 billion above what it owed token holders. The reserve mix is the part worth reading: beyond Treasury bills and repurchase agreements, it includes gold, bitcoin, secured loans, and other investments. Direct redemption with Tether is available only to verified customers, starting at $100,000; everyone else relies on exchanges and on-chain liquidity. USDT is not authorized under the EU's MiCA framework.

USDC is the second largest, with about $73 billion in circulation in October 2026. Circle publishes reserve information more frequently: a monthly examination by Deloitte, with daily reserve-fund reporting via BlackRock. At the end of August 2026, its $73.40 billion of reserves sat roughly 84.9% in a BlackRock-managed Treasury money market fund, 13.1% in bank cash, and 1.8% in Treasury bills. USDC has been an authorized e-money token under the EU's MiCA rules since July 2024. Redemption directly with the issuer goes through Circle Mint, which serves institutions rather than individuals.

The trade-off of this design is centralization. A fiat-backed stablecoin is only as trustworthy as its issuer's reserves, reporting honesty, and legal standing — and the issuer can freeze addresses when the law requires it.

2. Crypto-collateralized: software holds the collateral (DAI)

DAI, issued by the Maker Protocol (now part of the Sky ecosystem), has no company holding dollars in a bank. Instead, users lock cryptocurrency — such as ETH — into smart-contract vaults and borrow DAI against it. The protocol requires overcollateralization: typically at least 150% of the borrowed amount, with most users keeping closer to 200–300% to stay safe. If the collateral's value falls too far, the position is liquidated automatically and the collateral is sold to buy back the DAI.

About 4.58 billion DAI were in circulation as of September 2026, per a recent exchange risk disclosure. The peg holds through overcollateralization plus arbitrage incentives, not through a promise of redemption with a company. The trade-off is capital inefficiency — you must lock up far more value than you borrow — and exposure to crypto-market crashes, which is exactly when liquidations cascade.

3. Algorithmic: code was supposed to hold the peg (TerraUSD)

The third design tried to hold a dollar peg with no full reserves at all. TerraUSD (UST) was kept near $1 by a mint-and-burn arbitrage with its sister token LUNA: burn UST to mint LUNA when the price slipped, and the reverse when it rose. In May 2022 the mechanism broke under a run. UST fell from its peg to near zero within days, LUNA's supply hyperinflated as redemptions minted more of it, and an estimated $40 billion of value was destroyed. The lesson the industry took from it — and regulators codified afterward — is blunt: a peg backed by nothing but demand for the system itself has no floor when demand disappears.

Why Pegs Sometimes Slip Briefly

Even well-reserved stablecoins wobble. In March 2023, USDC fell to about $0.86–0.87 after $3.3 billion of its reserves were found to be held at the failed Silicon Valley Bank. It recovered fully once redemptions resumed. The episode is instructive: a brief depeg is not the same as a collapse. What separated USDC's wobble from TerraUSD's death spiral was that the reserves existed and redemptions restarted. When evaluating any depeg headline, the question to ask is whether the backing is intact and redeemable — not how far the price moved on one exchange.

A Checklist Before Trusting Any Stablecoin

Five questions, in order of importance:

1. What exactly is in the reserve, and who verified it? Cash and short-dated Treasuries behave differently from gold, bitcoin, and loans in a panic. And an attestation — a point-in-time confirmation by an accounting firm — is not the same as a full audit of the issuer's systems and controls. Know which one you are reading.

2. How often is it reported? Monthly reporting with daily fund data (USDC's pattern) gives you a fresher picture than quarterly reporting (USDT's pattern). Stale numbers are where surprises hide.

3. Who can redeem, and on what terms? If only verified institutions can redeem directly, your exit in a crisis runs through exchanges and market liquidity — which is thinnest exactly when you need it most.

4. What does the regulator say? The U.S. GENIUS Act, signed July 18, 2025, set federal standards for large stablecoin issuers: 100% backing in liquid assets such as cash or short-dated government securities, monthly public reserve disclosure, holder priority over general creditors in insolvency, and federal or state licensing. In the EU, MiCA authorization is the equivalent marker. A stablecoin's regulatory standing tells you which rulebook its issuer must follow.

5. How deep is the liquidity where you actually use it? The peg that matters is the one on your chain and your exchange. USDT dominates trading pairs and the Tron network; USDC leads in regulated and institutional flows — its 2025 on-chain transaction volume of $18.3 trillion surpassed Tether's $13.3 trillion for the first time since 2019.

What Stablecoins Are Actually Used For

Three uses account for most of the volume: a base pair for crypto trading (parking value between trades without touching a bank), cross-border transfers and dollar savings in countries with unstable local currencies, and on-chain settlement for businesses. None of these uses requires believing a stablecoin is "safe" in any absolute sense — they require judging, case by case, whether the specific token's backing and redemption path are adequate for the amount and the time horizon involved.

Sources and Further Reading

Circulation and reserve figures above come from recent issuer disclosures and independent coverage of them: USDT reserve and circulation data, USDC reserve and circulation data, a reconciliation of USDC's reserve fund against SEC filings, background on the GENIUS Act's stablecoin standards, a timeline of the TerraUSD collapse, and an exchange risk disclosure describing DAI's collateral model. Figures change with each reporting cycle; check the latest attestation before relying on any number.

The peg is a promise. Read the reserves before trusting the promise.