How Stablecoins Keep Their Peg
๐ 8 min read
Quick Answer
A stablecoin is only useful if one token reliably equals one dollar, but nothing forces a free-floating token to hold that price. The peg is held by deliberate mechanisms: real reserves you can redeem against, over-collateralization, or arbitrage. Understanding how the peg is maintained tells you exactly how fragile or sturdy each stablecoin really is.
๐ต The mental model
A peg is like a boat tied to a dock. A fiat-backed coin is roped directly to the dollar by redeemable reserves, a short, strong rope. An algorithmic coin is held in place only by everyone believing it will stay, no rope at all, just balance. When a storm hits, you find out which boats were actually tied down.
Reserves and redemption (fiat-backed)
The strongest peg comes from real backing: the issuer holds roughly one dollar of cash and safe bonds for every token. Big players can redeem tokens for real dollars at $1, so if the price dips, arbitragers buy cheap tokens and redeem them for a profit, pushing the price back up. The peg holds because the dollars are really there.
Over-collateralization (crypto-backed)
Coins like DAI cannot hold dollars, so instead they lock up MORE than a dollar of crypto for each token, say $150 of ETH per $1 of DAI. If collateral falls in value, it is automatically sold to keep the system solvent. The buffer absorbs crypto's volatility, which is why these coins stay over-collateralized by design.
Arbitrage and market incentives
In all healthy stablecoins, arbitrage is the engine that restores the peg: whenever the price drifts from $1, traders are financially rewarded for pushing it back, by redeeming, minting or trading. This only works if the underlying redemption or collateral promise is credible. Take away the credible backing and arbitrage cannot save the peg.
Why algorithmic pegs broke
Algorithmic stablecoins like TerraUSD tried to hold $1 with no real reserves, using a partner token and code-driven incentives. It worked while confidence lasted, then collapsed in days when a "bank run" overwhelmed the mechanism, a "death spiral". The lesson: a peg backed only by belief is not stable, it is a confidence game waiting to break.
๐ Key takeaway
Stablecoins hold their $1 peg through real backing plus arbitrage: fiat-backed coins by redeemable reserves, crypto-backed coins by over-collateralization that absorbs volatility. Arbitragers profit from pushing the price back to $1, but only if the backing is credible. Algorithmic coins with no real reserves (TerraUSD) proved a belief-only peg can collapse overnight.
Why this matters for you
For Asian users holding stablecoins as digital dollars, the pegging mechanism is the difference between safe savings and a wipeout. Many regional savers learned this painfully when TerraUSD collapsed. Knowing how a coin holds its peg, real reserves versus pure algorithm, is the single most important safety check before trusting it with money.
Frequently asked questions
What makes a stablecoin worth exactly $1?โผ
A credible backing plus arbitrage. If big holders can redeem tokens for $1 of real reserves (or claim over-collateralized crypto), traders profit by pushing any off-peg price back to $1. The peg holds because the backing behind that promise is real.
What is a stablecoin "depeg"?โผ
When a stablecoin trades meaningfully away from its $1 target, up or, dangerously, down. Brief depegs can happen under stress and recover (USDC in 2023); a permanent collapse happens when the backing fails (TerraUSD). Depegs reveal whether the peg was truly backed.
Why did TerraUSD (UST) collapse?โผ
It was algorithmic, with no real dollar reserves, relying on a sister token and market confidence to hold $1. When large withdrawals broke that confidence, the mechanism spiraled and both tokens crashed to near zero in days, wiping out tens of billions.
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๐ Sources & further reading
Authoritative references and primary sources used in this guide.