Getting Started
What Is a Stablecoin Depeg? Peg Mechanics, Cases and Principles
"Stable" is a design goal, not a guarantee. Learn what holds fiat-backed, collateralised and algorithmic pegs together, why UST and USDC ended so differently, and how to reduce your exposure.
"Stable" is in the name, but it describes a design goal, not a guarantee. When the market price drifts noticeably from the value a coin claims to track — usually one US dollar — and stays there, that is a depeg.
For a beginner, the useful thing is not memorising past events but understanding what actually holds each peg together, because the mechanism determines how a coin behaves under stress.
How pegs are maintained
| Type | How the peg is held | Main source of risk |
|---|---|---|
| Fiat-reserve backed | The issuer holds cash and short-term instruments and promises redemption | Reserve quality, custodian banks, whether redemption stays open |
| Crypto-collateralised | Overcollateralised crypto backs it, with liquidations adjusting supply | Collateral crashing, crowded liquidations, oracle failure |
| Algorithmic | Mint-and-burn arbitrage incentives adjust supply | Incentives fail when confidence breaks, risking a death spiral |
A practical test: ask "if I want my dollar back, who ultimately owes it to me?" For fiat-reserve coins that points to the issuer and its reserves; for collateralised ones to a smart contract and its collateral; for algorithmic ones there is often no identifiable payer at all — which is precisely the fragility.
Why depegs happen
Doubts about reserves. When the market suspects reserves are short, of poor quality, or that redemption is obstructed, holders race to sell first.
A broken redemption channel. Reserves may exist while a custodian bank fails or redemptions pause, producing a short-term discount. In March 2023 USDC briefly traded below a dollar after a bank holding part of its reserves failed, then returned to the peg once deposit access was assured.
Mechanism failure. Algorithmic designs depend on the market being willing to arbitrage. During the UST collapse in May 2022 the incentive structure accelerated selling instead, and the coin fell alongside its paired token without recovering.
Liquidity drying up. On a specific exchange or pair, thin books can push price away briefly without indicating a market-wide depeg.
The critical distinction: a temporary discount that recovers and a mechanism failure that goes to zero are entirely different events. The first tests your tolerance; the second causes permanent loss.
Two historical cases, two outcomes
UST (May 2022): algorithmic by design, never recovered after depegging, and collapsed together with its paired token — the textbook mechanism failure.
USDC (March 2023): fiat-reserve backed, briefly fell below the peg amid doubts triggered by a reserve bank's failure, then returned near a dollar once redeemability became clear.
Both are called depegs and the outcomes diverged completely. The difference was not how far price fell, but whether redeemable assets stood behind it.
Reducing your exposure
- Know which type you hold. Check the issuer, what backs it, and whether attestations are published regularly. Our guide on reading proof of reserves covers what such reports do and do not prove.
- Do not concentrate everything in one stablecoin. Diversification does not remove risk, but it avoids a single point of failure.
- Be sceptical of unusually high yields. A product marketed as both stable and high-yielding is generally paying you for risk you have not identified.
- Match the coin to the use case. Short-term working capital and long-term parked funds warrant different risk tolerances.
- Watch the custody layer separately. A sound coin held on an unsound platform is still exposed — see our wallet types guide.
When a depeg is happening, do not rush
Separate three questions first: is the deviation market-wide or one exchange's spread? Has it lasted hours or minutes? Has the issuer or platform said anything officially?
Order books during panic are thin, so market orders can fill far worse than the displayed price — exactly when slippage does the most damage. Depeg events are also peak season for fraud, typically pitched as "emergency conversion assistance" or an "official compensation channel."
FAQ
Is any stablecoin completely safe?
No. The types differ in where the risk sits: with the issuer and banking system, with contracts and collateral, or with mechanism and confidence.
Do depegs always recover?
No. Coins with real backing have a basis for recovery; mechanism failures may never recover. One past recovery does not predict the next event.
What is the difference between USDT and USDC?
Both are fiat-reserve types, but they differ in issuer, reserve composition and disclosure practice. For the basics, start with what USDT is.
Is holding on an exchange safer?
That is a different layer of risk, not the same one. Exchange custody depends on the platform's solvency and withdrawal policy, which is unrelated to the peg mechanism.
Can I treat stablecoins as savings?
They are designed as a stable unit of account and transfer medium, not a principal-protected product. There is no deposit insurance and no promised yield — treating one as a savings account is a common misunderstanding.
Official sources and verification note
Reserve composition, disclosure cadence and regulatory treatment continue to change. Information here was verified on 2026-08-22 (UTC+8); historical cases illustrate mechanics and do not predict future behaviour. This article is educational and not investment advice; crypto trading can lose your entire principal. Not intended for residents of mainland China.