Stablecoins Explained: How They Hold $1 — and When They Don't

Stablecoins are crypto's quiet giant. They settle trillions of dollars a year, more than most card networks, yet most people couldn't explain what actually keeps a digital token worth exactly one dollar. The answer matters, because not all stablecoins are built alike — and the differences decide what happens to your money in a crisis.

What a stablecoin is

A stablecoin is a token designed to track a fixed value, almost always the US dollar. Traders use them to park profits without leaving crypto, or to run strategies like dollar-cost averaging. People in countries with weak currencies use them as digital dollars. DeFi uses them as its base money. None of that works unless the peg holds.

Three ways to hold a peg

1. Fiat-backed: a dollar in the bank for every token

Tether (USDT) and USD Coin (USDC) dominate the market with this model. The issuer holds reserves — cash and short-term US Treasury bills — and promises to redeem every token for $1. Arbitrage does the rest: if the price slips to $0.99, traders buy tokens and redeem them for a dollar, pushing the price back.

The catch is trust. You are trusting that the reserves are real, liquid, and reachable. This is why reserve reports matter — and why USDC briefly traded at $0.88 in March 2023, when some of its reserves were caught in the collapsed Silicon Valley Bank. The peg recovered within days, but the lesson stands: a fiat-backed stablecoin is exactly as solid as its banking arrangements.

2. Crypto-backed: overcollateralized on-chain

DAI, the longest-running example, is backed not by bank dollars but by crypto locked in smart contracts — and deliberately overbacked: roughly $150+ of collateral for every $100 of stablecoin, because the collateral itself is volatile. If collateral value falls too far, it's automatically liquidated to protect the peg.

The appeal is transparency — anyone can audit the collateral on-chain in real time. The cost is capital inefficiency and exposure to crypto market crashes, plus the irony that much of DAI's collateral today is itself USDC.

3. Algorithmic: confidence backed by code

Algorithmic stablecoins try to hold the peg with supply mechanics alone — minting and burning a sister token to absorb demand swings, with little or no hard collateral. The model has a catastrophic failure mode: when confidence breaks, the mechanism that should restore the peg accelerates the collapse instead.

That's not hypothetical. In May 2022, TerraUSD (UST) — then a top-ten asset — went from $1.00 to under $0.10 in a week, erasing about $40 billion. Every major purely algorithmic stablecoin has eventually broken.

How to judge a stablecoin in five minutes

• What backs it? Cash and T-bills are the gold standard. Crypto overcollateralization is acceptable and transparent. "Algorithm" is a red flag.
• Can you see the reserves? Monthly attestations by known accounting firms, or live on-chain collateral. No reports, no trust.
• Can it be redeemed, and by whom? A peg without a working redemption path is a promise without a mechanism.
• Has it survived stress? Pegs are tested in crashes, not calm markets. A coin that has held through several crises has proven something a new one hasn't.
• Who regulates the issuer? Regulation is imperfect, but an issuer with licenses and audit obligations has more to lose by lying.

The takeaway

"Stable" describes the goal, not a guarantee. Fiat-backed coins carry banking and trust risk, crypto-backed coins carry market risk, and algorithmic coins have a track record of dying suddenly. For most uses, stick to the largest, most transparent, redemption-tested options — and treat any stablecoin paying suspicious yield as the risk asset it really is.