Stablecoins Explained: USDT, USDC, DAI, and Why They Aren't All Equal

A stablecoin is the most underrated piece of crypto infrastructure. It also has the most variable risk profile of anything you'll touch. The shorthand "1 USDT = $1" hides huge differences in what kind of dollar that one really is.

Why stablecoins exist

Settle a $50,000 trade between two crypto traders without a stablecoin and you're forced to either (a) use a volatile asset like BTC, where the price between agreeing and settling can move 1%, or (b) leave crypto rails entirely and use the banking system, which is slow, expensive, and not 24/7. Stablecoins solve this by giving you a dollar-denominated asset that moves on crypto rails.

That's it. The entire reason stablecoins are >$200B in market cap is that they let you exit volatility without exiting the crypto financial system. Every other use case (payments, remittances, savings) sits on top of this primary one.

Three ways to make a stablecoin

The mechanism that holds the price near $1 matters more than the ticker. There are three families, with very different failure modes.

1. Fiat-backed (USDT, USDC). A company holds real dollars (and short- duration treasuries) in a bank account, and issues a token redeemable 1:1 for those dollars. The token's price stays near $1 because arbitrageurs can always buy below $1 and redeem for $1, or sell above $1 and create new tokens at $1. The risk is concentrated entirely in the issuer: are the reserves really there, are they liquid, can you actually redeem in stress?

2. Crypto-backed (DAI, GHO). A smart contract holds excess crypto collateral (e.g., $150 of ETH backing every $100 of DAI) and issues stablecoins against it. If ETH falls, the contract liquidates collateral to maintain the peg. No central issuer, but you trust the smart contract code, the price oracle, and the governance.

3. Algorithmic (mostly dead). A protocol tries to maintain a peg through supply mechanics, minting/burning tokens to push the price back to $1. Terra/UST collapsed in 2022 in a $40B unwind because the mechanism only works under bullish reflexive conditions. When the reflexivity reverses, the system enters a death spiral. Treat these as unbacked even if the marketing says otherwise.

How to read a fiat-backed stablecoin's risk

Fiat-backed dominates the market (USDT + USDC are >85% of stablecoin supply). To evaluate one, look at exactly three things:

1. Reserve composition. Cash and short T-bills are the gold standard. Commercial paper, corporate bonds, or "secured loans" are yellow flags. Anything described as "Bitcoin reserves" or "secured loans to affiliated entities" is a red flag.
2. Auditor. Big-four attestations (USDC) are stronger than smaller- firm attestations (USDT). An attestation is not a full audit, but regular monthly attestations from a reputable firm beat quarterly ones from a no-name.
3. Redemption mechanism. Can you, personally, redeem at $1, or is redemption restricted to whitelisted institutional partners with minimum sizes? Most stablecoins are the latter; that's fine, but it means the peg depends on those partners' arbitrage incentives, not on retail being able to walk in and demand $1.

USDT historically traded as low as $0.95 during the 2018 crisis on FUD about reserves. USDC briefly broke peg to $0.87 in March 2023 during the SVB collapse because some of its reserves were held there. Both recovered. Both also reminded everyone that "stable" is not the same as "risk-free".

A common mistake: treating stablecoins as cash

If you hold $100,000 in USDT, you do not have $100,000 in cash. You have a $100,000 unsecured claim on Tether Limited, denominated in dollars, which trades close to $1 most of the time. The difference matters when:

• The issuer is sanctioned, hacked, or insolvent
• The chain the token lives on has issues (USDT-ERC20 vs USDT-TRC20 vs USDT-Solana are technically different tokens with different reserves per chain in some setups)
• The exchange you hold it on has issues, that adds another layer of counterparty risk on top of the issuer risk
• Stress concentrates redemption requests faster than the issuer can process them

This is especially important for sizing: don't treat a giant stablecoin position as "no exposure". You're long the issuer, long the banking system that holds the reserves, and long the chain it lives on.

Mental model, stablecoins as bearer money-market shares

A money-market mutual fund pools cash, holds short-duration instruments, and issues shares that aim to maintain a constant $1 NAV. Sometimes, rarely, they "break the buck", and shares trade below $1. A fiat-backed stablecoin is functionally the same thing, but issued in bearer form (whoever holds the token has the claim) and tradeable 24/7 on-chain. Once you see them this way, you start asking the right questions: what's in the underlying portfolio, who's the manager, what's their track record under stress.

Why this matters for trading

Most active crypto trading is denominated in stablecoins, not BTC. Your PnL ledger, your margin balance, your "cash" position in a perp account all of these are stablecoin-denominated. A 5% depeg event in your quote currency wipes out months of trading profits silently while your PnL dashboard happily shows the same number of "dollars". Pick your quote currency deliberately, and consider holding multiple stablecoin types if you're carrying significant balances.

Takeaway

Stablecoins make modern crypto trading possible. But "stable" is a marketing claim, not a property, what matters is what backs the token, who issues it, and how redemption works under stress. Fiat-backed beats crypto-backed beats algorithmic, in that order. Your stablecoin balances are concentrated counterparty exposure, not cash. Size them accordingly.