How stablecoins maintain their peg

A stablecoin is a crypto token designed to hold a steady value against a reference asset, most often one US dollar or one euro. The “peg” is that target price. Keeping a token close to its peg is not automatic: it depends on a mix of reserves, arbitrage incentives, and design rules that either work well under stress or break down. This article explains the main mechanisms neutrally, so you can see why some pegs are sturdier than others.

What “maintaining a peg” actually means

No stablecoin is legally guaranteed to trade at exactly its target on every venue at every second. In practice a peg is “held” when the market price stays within a narrow band of the target and reliably returns to it after small deviations. Two forces do the work:

• Redemption or backing — a promise (contractual or mechanical) that each token can be exchanged for something worth the peg.
• Arbitrage — traders who profit by buying the token when it is cheap and redeeming it, or minting new tokens when it is expensive and selling, pushing the price back toward target.

When both forces are strong and credible, small deviations are corrected quickly. When either weakens, the band widens and the peg can slip.

Fiat-backed stablecoins: redemption at par

The most common design holds reserves of cash and short-dated government debt and promises that authorised parties can redeem tokens for fiat at par. If the token trades below the peg, an arbitrageur can buy it cheaply on the market and redeem it with the issuer for the full peg value, pocketing the difference. That buying pressure lifts the price. If it trades above the peg, new tokens can be minted by depositing fiat and sold into the market, adding supply and pushing the price down.

The mechanism only works as well as the redemption promise behind it. What matters is whether reserves are genuinely liquid, whether redemption is available quickly and to enough participants, and whether the terms can be paused. Because these details vary between issuers and can change, readers should check each issuer’s own reserve reports and redemption terms directly rather than assuming they are identical. For more on why published reserve reports have limits, see what reserve attestations do and don’t prove.

Crypto-backed stablecoins: overcollateralisation

Some stablecoins are backed not by fiat in a bank but by other crypto assets locked in smart contracts. Because that collateral is itself volatile, these systems require overcollateralisation: a user might lock up collateral worth more than the stablecoins they mint, creating a buffer against price swings. If the collateral’s value falls toward the amount borrowed, the position is automatically liquidated — sold off to keep the system solvent.

Here the peg is defended by on-chain rules rather than a bank redemption. Stability depends on the size of the buffer, how quickly liquidations happen, and whether markets stay liquid enough to sell collateral during a sharp fall. In severe, fast declines, liquidations can lag or clear at bad prices, which stresses the peg. The trade-off is transparency and permissionless access in exchange for exposure to crypto-market volatility. The comparison of stablecoin types goes into these differences in more detail.

Algorithmic stablecoins: incentives instead of backing

A third approach tries to hold the peg with little or no full backing, relying instead on algorithms that expand and contract supply, often paired with a second “absorber” token. In theory, when the stablecoin trades below target the protocol reduces supply or offers arbitrage into the companion token to push the price back up; when it trades above target it expands supply.

These designs carry a well-documented structural risk: the mechanism can enter a self-reinforcing downward spiral. If confidence falls and holders rush to exit, the supporting token can be minted in large quantities, collapsing its own value and removing the very support the peg relied on. The most cited real-world example is the collapse of the UST algorithmic stablecoin and its companion token in May 2022, which lost its peg and did not recover. It remains a standard case study in how quickly a confidence-based peg can unwind once redemption pressure exceeds what the mechanism can absorb.

Why arbitrage sometimes isn’t enough

Arbitrage is the quiet engine behind most healthy pegs, but it has preconditions that are easy to overlook. For a trader to profitably buy an under-peg token and redeem it, redemption has to be open to them, fast, and cheap enough that the profit survives fees and delays. If redemption is restricted to a handful of large approved partners, ordinary market participants cannot close the gap themselves and must wait for those partners to act — which they will only do if they, too, trust the redemption.

Timing matters as much as access. Arbitrage corrects prices over minutes and hours; a fast, panicked sell-off can move the market price far below target before anyone completes a redemption cycle. During that window the token can trade at a visible discount even while the backing is intact. This is why a temporary discount is not automatically evidence of insolvency, and why a token sitting exactly at target is not automatically proof of health — the informative question is whether the arbitrage loop can actually run at scale, right now, for enough participants.

It also helps to separate the peg from yield. Some stablecoins pass through interest earned on reserves or offer rewards elsewhere in a protocol, but a yield is a separate feature layered on top of the peg — not part of what holds the price at target. Confusing an attractive yield with peg strength is a common mistake; the return says little about whether you can get par value back when you want it.

The forces that break a peg

Whatever the design, pegs tend to come under pressure through a common set of channels:

• Loss of confidence in reserves or collateral — if holders doubt they can redeem at par, selling can overwhelm the arbitrage that normally restores the peg.
• Redemption friction — if redemption is slow, limited to a few large parties, gated by minimums, or can be paused, the market price can drift well away from target before arbitrage kicks in.
• Liquidity gaps — a peg needs deep, two-sided markets. Thin liquidity, especially during broader market stress, magnifies deviations.
• Correlated stress — when a stablecoin’s collateral or the wider crypto market falls at the same time as redemption demand rises, defensive mechanisms can be overwhelmed together.
• Concentration and counterparty risk — reserves held with a single bank or custodian can transmit that institution’s troubles straight to the peg.

A brief loss of peg is not always a permanent failure; well-backed tokens have deviated and then recovered as redemption reasserted itself. The key question is always whether a credible, fast path back to par exists.

How the mechanisms compare

What this means

The takeaway is not that one design is “safe” and another is not, but that a peg is only as strong as the mechanism and incentives holding it in place. A price of exactly one dollar on a screen tells you little on its own; what matters is whether a fast, credible route back to par exists when many holders want out at once. Because reserve composition, redemption terms, and legal protections differ between issuers, the practical step is to read each issuer’s own disclosures and terms directly rather than relying on the peg’s appearance.

Rules covering stablecoins differ by jurisdiction and continue to change, so nothing here is investment, legal, or tax advice; for decisions about your own situation, consult a qualified professional. To see how the underlying models differ, read fiat-backed vs crypto-backed vs algorithmic stablecoins, and for the policy backdrop see how stablecoin regulation is developing.