What are Stablecoins? USDT, USDC, and DAI

Crypto is volatile. Bitcoin can drop 15% in a day. Ethereum has crashed 80% in a bear market. If you're a trader who just took profit on a position, you don't want to sit in BTC while you decide your next move. You want somewhere to park value without worrying about a 3 AM flash crash.

Stablecoins solve this. They're crypto tokens pegged to a stable reference — almost always the U.S. dollar. One USDT is designed to equal one dollar. One USDC is designed to equal one dollar. The mechanism that maintains that peg varies dramatically between stablecoins, and that variation is where the risk hides.

As of early 2025, the total stablecoin market cap exceeds $150 billion. USDT alone accounts for over $110 billion. Stablecoins settle more value on-chain than Visa processes globally — not because consumers are buying coffee with USDC, but because traders, DeFi protocols, and cross-border payment rails have made stablecoins the default unit of account for the entire crypto economy.

Tether (USDT) is the oldest and largest stablecoin. For every USDT in circulation, Tether Holdings claims to hold equivalent assets in reserve — primarily U.S. Treasury bills, overnight reverse repurchase agreements, and cash. Their reserve attestations, published quarterly, show a portfolio heavily weighted toward short-duration government debt. The market trusts this claim enough to maintain the peg through multiple crises. But Tether has never submitted to a full independent audit — only attestations from accounting firm BDO Italia. That distinction matters. An attestation confirms a snapshot; an audit confirms the process.

USD Coin (USDC) is issued by Circle and backed by cash and short-dated U.S. Treasuries held at regulated financial institutions. Circle publishes monthly reserve reports audited by Deloitte. In March 2023, USDC briefly depegged to $0.87 after Silicon Valley Bank (where Circle held $3.3 billion in reserves) collapsed. The peg recovered within 48 hours once the FDIC guaranteed SVB deposits — but those 48 hours demonstrated that even "safe" stablecoins carry counterparty risk tied to the traditional banking system.

Both USDT and USDC function similarly from a user perspective: dollar-denominated tokens on multiple chains. The difference is in the risk profile beneath the surface.

DAI takes a radically different approach. Instead of dollars in a bank, DAI is backed by crypto assets locked in smart contracts on Ethereum. You deposit ETH (or other approved collateral) into a MakerDAO vault, and the protocol lets you mint DAI against it — but only up to a fraction of the collateral's value. Deposit $150 worth of ETH, mint up to $100 of DAI. That 150% ratio is the safety margin.

If your collateral value drops below the minimum ratio, the protocol automatically liquidates your position — selling your ETH at a discount to repay the DAI debt. This mechanism kept DAI stable through the March 2020 crash (when ETH fell 43% in a single day) and through the 2022 bear market. It's not perfect — during extreme volatility, liquidation cascades can create their own selling pressure — but the overcollateralization model has survived every stress test so far.

The trade-off is capital inefficiency. Locking $150 to create $100 of stablecoins means a third of your capital is dead weight. That's the price of decentralization without a trusted issuer. MakerDAO has partially addressed this by accepting USDC as collateral (which is ironic — a decentralized stablecoin partially backed by a centralized one) and by onboarding real-world assets like U.S. Treasuries through the Spark protocol.

On May 7, 2022, the algorithmic stablecoin UST began losing its dollar peg. By May 12, it was worth $0.10. Its companion token LUNA fell from $80 to fractions of a penny. Combined market cap destruction: over $40 billion. Savings accounts wiped out. Suicide hotline posts pinned on crypto subreddits.

Algorithmic stablecoins maintain their peg through code, not collateral. UST's mechanism: if UST drops below $1, you can burn it for $1 worth of newly minted LUNA. The arbitrage should restore the peg. But in a bank-run scenario, everyone burns UST simultaneously, flooding the market with LUNA, crashing LUNA's price, which destroys confidence in UST further, which triggers more burns. The death spiral is reflexive and, once started, impossible to stop.

The UST collapse wasn't a black swan. The vulnerability was known and publicly documented. Algorithmic stablecoins had failed before — Iron Finance collapsed in June 2021 using a nearly identical mechanism. But Anchor Protocol was paying 19.5% APY on UST deposits, and yield has a way of making people forget about risk.

On GaiaEx, USDC and USDT serve as the primary quote currencies for spot and perpetual markets. Every trading pair is denominated against one of them. When you take profit on a BTC trade, you're receiving stablecoins into your non-custodial wallet — no conversion to fiat required, no bank transfer delay.

The practical question is which stablecoin to hold between trades. USDT has deeper liquidity globally. USDC has stronger auditing and U.S. regulatory alignment. Some traders split their idle capital across both to diversify issuer risk — a reasonable approach given that even USDC temporarily depegged during the SVB crisis. Neither is risk-free. Both are dramatically safer than holding an algorithmic alternative.