How stablecoins maintain their peg: convertibility, collateral, and arbitrage

Stablecoins maintain their peg by making the “$1 trade” executable: someone can convert $1 of backing into 1 token (and back) quickly enough that arbitrage keeps the market price pinned near target. The design choice is which engine funds that trade, from stablecoin reserves and stablecoin redemption to onchain collateralization with liquidations or algorithmic supply changes.

Key Takeaways

• A stablecoin’s peg holds when convertibility and arbitrage can clear meaningful size during volatility, not because the token is “always worth $1.”
• Fiat-backed models defend $1 through stablecoin reserves and direct stablecoin redemption, which creates a tight mint-redeem arbitrage loop.
• Crypto-backed models defend $1 through overcollateralization and automated liquidations, which makes the system structurally short volatility.
• Algorithmic models defend $1 by changing supply via smart contracts, but the mechanism can fail reflexively when confidence breaks, as TerraUSD did in May 2022.

Understanding the stablecoin peg

A stablecoin peg is a target price the token is meant to trade at, usually one-to-one with the U.S. dollar. The important detail is that the market price is not a constant. It moves around the target and gets pulled back by a stabilizing trade that can be repeated all day in small clips and, during stress, in ugly size.

That is the microstructure frame that matters for anyone asking how does a stablecoin stay at 1 dollar. The peg is not a slogan. It is a promise that a conversion path exists: if the token prints $0.997 somewhere, there is a route to turn that discount into something closer to $1, and enough liquidity and operational capacity to do it before the discount becomes a narrative.

Two engines determine whether that route works. Engine one is the balance sheet, meaning stablecoin reserves for fiat-backed coins or onchain collateralization for crypto-backed designs. Engine two is the arbitrage loop, meaning how quickly and in what size market participants can mint, redeem, liquidate, or otherwise change supply to close the gap. When both engines work, stablecoins become the plumbing for onchain finance, supporting payments, lending, and trading where a stable unit of account is required.

This is also why “what is a stablecoin” is not just a definition question. It is a question about convertibility under stress. A peg that only works on calm days is not a peg, it is a marketing line waiting to meet a liquidity event.

Fiat-backed stablecoins and their peg

Fiat-backed stablecoins defend the peg by running a convertibility business. The issuer holds a reserve of fiat currency or traditional instruments such as government treasuries equal to the number of tokens in circulation, then offers minting and stablecoin redemption at (or near) $1. That convertibility is the stablecoin peg mechanism.

The sequence is mechanical:

1. A user deposits dollars with the issuer and receives newly minted stablecoins. 2. If the stablecoin trades below $1 on secondary markets, arbitrageurs can buy the discounted token and redeem it with the issuer for $1 of the underlying reserve. 3. If the stablecoin trades above $1, arbitrageurs can mint at $1 and sell at a premium, increasing supply where demand is paying up.

The peg strength is not just “is it backed.” It is whether the backing is available and whether the redemption rail clears quickly and predictably. If reserves are high quality and liquid, and redemption works smoothly, the market will do the rest because the arbitrage is clean. If redemption is slow, gated, or operationally constrained, the peg becomes a rumor that depends on confidence rather than a trade that can be executed.

This is where traders get tripped up. A fiat-backed stablecoin can be fully reserved on paper and still wobble if the market doubts access to those reserves in the moment that matters. The peg is enforced minute-by-minute by the ability to convert, not by a PDF.

Crypto-backed stablecoins and their peg

Crypto-backed stablecoins defend $1 by turning volatility into a risk-managed collateral system. Instead of offchain reserves, users lock decentralized digital assets into smart contracts and mint stablecoins against that collateral. Because the collateral is volatile, these systems require overcollateralization, meaning more than $1 of collateral is posted to mint $1 of stablecoins.

The peg maintenance loop is built around liquidation thresholds. When collateral value falls far enough, smart contracts automatically liquidate collateral to buy back stablecoins and keep the system solvent. That is the core stabilizer: the system forces deleveraging to keep the outstanding stablecoin supply covered.

This design has a very specific implication. The protocol is structurally short volatility. When the collateral dumps, the system must sell collateral into a falling market to defend the peg, and that can create cascades if liquidity is thin. The peg holds when three things line up at once: collateral buffers are large enough, price data is accurate enough to trigger liquidations at the right time, and liquidation execution can clear size without blowing through the market.

That is why oracle quality and liquidation mechanics sit next to collateral ratios on the checklist. Chainlink’s discussion of decentralized price feeds is aimed at this exact failure mode: if the protocol reads bad prices, it can liquidate when it should not, or fail to liquidate when it must. Either error can destabilize the peg.

Crypto-backed designs can be robust, but they are not “risk-free stable.” They are engineered stability that depends on automated risk controls working during fast markets.

Algorithmic stablecoins and their peg

Algorithmic stablecoins try to hold $1 without relying entirely on external reserves. The mechanism is supply management via smart contract algorithms: expand supply when the token trades above the peg, and contract supply when it trades below the peg by incentivizing burns or other supply-reducing actions.

Several families of designs show up repeatedly in the market. Bleap and The Block both describe models such as rebasing (supply adjusts across wallets), seigniorage-style systems (a stablecoin paired with a second token that absorbs volatility), and fractional or hybrid approaches that mix partial collateral with algorithmic controls. The common thread is that the peg is defended by incentives and reflexive expectations rather than a straightforward redemption claim on a reserve.

The canonical stress test is TerraUSD (UST) in May 2022. The system attempted to maintain parity through a mint-burn relationship with LUNA. When UST broke below $1, the mechanism pushed users to mint large amounts of LUNA to restore parity, which hyperinflated LUNA and accelerated the collapse. The episode wiped out over $40 billion in market value and permanently changed how traders price “algorithmic” as a risk label.

That is the confidence machine problem. Supply adjustment can look elegant when liquidity is deep and belief is intact. When belief breaks, the same mechanism can amplify the move away from $1 because the stabilizing trade stops being attractive. This is why hybrid models emerged in the 2023–2026 window, combining collateral buffers with algorithms to reduce the chance that the peg depends on one fragile incentive loop.

The role of arbitrage in peg stability

Arbitrage is the peg’s enforcement arm across every model. Traders and bots monitor stablecoin prices across centralized and decentralized venues and take the other side of small deviations, buying below peg and selling or redeeming at or above peg, or doing the reverse when the token trades rich.

The loop only works if it can be executed fast enough and in enough size. Chainlink is explicit that liquidity depth and the efficiency of minting and redemption processes determine whether arbitrageurs step in during volatility. If the trade is operationally blocked, the peg can drift because the market cannot close the basis.

A useful way to think about “how stablecoins keep their value” is to separate the theoretical arbitrage from the accessible arbitrage. If a stablecoin prints $0.99 and the only entities who can redeem at $1 are a small set of approved participants, everyone else is holding basis risk, not a free lunch. The market price will reflect that access constraint.

This is also why stablecoins can trade slightly off $1 for longer than people expect. The deviation is a fee for balance sheet risk, settlement time, transfer friction, or redemption uncertainty. When those frictions rise together, the stabilizing trade gets crowded out and the depeg becomes self-reinforcing.

For traders, the clean question is never “is it cheap at $0.99.” The question is whether the arbitrage path is open, how long it takes, and whether it clears size when everyone wants the same exit.

Risks of de-pegging and future stability

De-pegging happens when the stabilizers are overwhelmed. The sources converge on three broad catalysts: liquidity crises that resemble bank runs, smart contract vulnerabilities, and oracle manipulation. Each one breaks a different link in the chain, but the ugly events tend to stack failures.

Liquidity crises are the simplest to understand. If many holders try to redeem at once and the issuer cannot meet near-term redemption demands with liquid assets, the market price can gap down as users sell on secondary markets to get out. Even a fully backed structure can wobble if the backing is tied up in longer-dated or less liquid instruments and the market doubts immediate convertibility.

Smart contract and oracle failures are the onchain equivalents of a broken balance sheet. A bug can drain collateral or allow supply to inflate, and manipulated price inputs can trigger incorrect liquidations or prevent necessary ones. Chainlink’s emphasis on tamper-resistant data and Proof of Reserve is aimed at reducing these specific attack surfaces, including giving the market better visibility into stablecoin reserves.

The direction of travel is toward more transparency and more robust plumbing. Fully collateralized models, clearer auditing, and stronger data infrastructure are becoming the baseline expectations as stablecoins evolve from a trading convenience into a settlement layer for onchain finance. Near the end of any evaluation, the broader question returns: is this stablecoin a credible unit of account when the exit door gets crowded.

The Take

I’ve watched traders treat a stablecoin at $0.99 like a bargain, then realize too late they don’t have the rail that matters: stablecoin redemption at par. If the only people who can close the loop are a small set of counterparties, everyone else is just long a spread that can widen when liquidity disappears.

The expensive misconception is “backed” as a binary. After the TerraUSD collapse in May 2022, the market got a clean reminder that the peg is a tradable microstructure problem. The real test is convertibility plus arbitrage capacity under stress. When those two engines can’t clear size, the peg stops being a price target and turns into a debate.

Sources

• Chainlink
• Shift Markets
• Bleap Finance
• The Block