How Stablecoins Hold Their Peg — and What Happens When They Don’t

Most cryptocurrencies are prized for their volatility. A stablecoin is the opposite: a token engineered to stay close to a fixed value, almost always one US dollar. That single design goal shapes everything about how these assets work — and everything about how they can fail. This guide explains, in plain terms, what keeps a stablecoin near its target, why a peg can slip, and how to think about the risks before you rely on one.

What a stablecoin is, and why it exists

A stablecoin is a crypto token whose creators aim to keep its market price pinned to a reference value, most commonly the dollar but sometimes another currency or, more rarely, a commodity such as gold. The word “peg” simply describes that intended one-to-one relationship.

The appeal is practical. Traders use stablecoins as a place to sit between positions without cashing out to a bank. People in the wider ecosystem use them to move value across borders and between exchanges quickly, and to interact with lending, trading and other on-chain applications that expect a steady unit of account. In short, a stablecoin tries to offer the convenience of crypto rails with the price behaviour of ordinary money. You can explore individual tokens across our stablecoins coverage.

The main types of stablecoin

Not all stablecoins hold their peg the same way. The differences matter enormously, because each design carries its own strengths and failure modes.

Fiat-backed (reserve-backed)

These are the most familiar. For every token in circulation, the issuer claims to hold an equivalent amount of value in reserves — typically cash and short-term, cash-like assets — held with banks or custodians. Tether (USDT) and USD Coin (USDC) are the best-known examples of this model. The core promise is redemption: eligible holders can, in principle, exchange tokens for the underlying currency, and that convertibility is what anchors the price.

Crypto-collateralised (over-collateralised)

Here the backing is other cryptocurrency rather than bank deposits. Because crypto collateral is itself volatile, these systems are deliberately over-collateralised: users lock up more value than they mint, leaving a buffer that absorbs price swings. DAI is a widely used example. Automated rules liquidate collateral if its value falls too far, aiming to keep every token fully covered on-chain.

Algorithmic

Algorithmic designs try to hold a peg through code and market incentives rather than by holding an equivalent reserve. They typically expand or contract supply, or lean on a linked token, to nudge the price back to target. It is worth being blunt here: purely algorithmic and lightly collateralised models have a poor track record. Several have de-pegged sharply and, in some cases, collapsed entirely when confidence evaporated faster than the mechanism could respond. Treat this category with particular caution.

How the peg is actually maintained

Whatever the label, a peg holds for one underlying reason: market participants believe a token is reliably worth its target and act on that belief. The mechanisms simply make that belief credible.

• Redemption and issuance. For reserve-backed tokens, the ability to create new tokens by depositing dollars, and to redeem tokens for dollars, is the anchor. If a token trades slightly below target, someone who can redeem at full value has an incentive to buy the cheap tokens and cash them in, nudging the price back up.
• Arbitrage. Across every design, traders profit by buying below peg and selling above it. This constant activity is the everyday force that keeps small deviations small.
• Collateral and liquidation. In over-collateralised systems, automated liquidations top up the backing when markets move, preserving the buffer that supports each token.
• Deep liquidity. Large, liquid trading venues let arbitrage happen at scale without a single trade moving the price. Thin markets make pegs fragile.

What makes a peg break

Even a well-designed stablecoin can wobble, and history shows that even reserve-backed tokens can briefly trade away from their target under stress. A break usually traces to one or more of the following.

• Reserve doubts. If holders question whether the reserves truly exist, are of high quality, or are fully accessible, confidence can drain quickly. A stablecoin is ultimately a promise, and promises are only as good as their credibility.
• Redemption stress. A peg leans on the belief that redemption works. If many holders try to exit at once — a classic run — or if redemption is paused, slowed or restricted, that belief can crack and the price can slide.
• Liquidity crunches. When trading dries up, arbitrageurs cannot cheaply push the price back to target, so even a modest imbalance in supply and demand can open a visible gap.
• Collateral failure. For crypto-backed tokens, a violent, fast market drop can overwhelm liquidations, eroding the buffer that keeps each token covered.
• Mechanism breakdown. For algorithmic models, the incentives that are meant to restore the peg can invert under panic, accelerating a decline rather than arresting it.

Some de-pegs are temporary and recover within hours or days once confidence or liquidity returns. Others are permanent. The difference often comes down to whether real, redeemable value stands behind the token.

How to assess stablecoin risk

You cannot eliminate stablecoin risk, but you can weigh it. A few practical questions help.

• What backs it, and how? Reserve-backed, over-collateralised and algorithmic tokens are not interchangeable. Know which model you are holding.
• How transparent is the issuer? Look for clear, regular disclosure about reserves or on-chain collateral. Vagueness is a warning sign.
• Can you actually redeem? Understand who may redeem, under what terms, and whether redemption has ever been restricted.
• How deep is its liquidity? A token that trades thinly is more likely to gap under stress.
• What is the track record? Has the token held its peg through past turbulence, or has it slipped before?

No stablecoin is entirely risk-free, and “stable” describes an aim, not a guarantee. For more on how we approach these assets and what we look for, see our methodology. Treat the peg as a claim to be examined, not a promise to be trusted blindly.

This article is for informational purposes only and is not financial advice.