Stablecoins are cryptocurrencies designed to maintain a consistent value, usually pegged to a fiat currency like the US dollar. Because they sit on blockchains while behaving like familiar money, they have become foundational infrastructure for decentralized finance, trading, and cross-border payments. But “stablecoin” is not a single technology — it is a goal achieved through very different mechanisms, each with its own strengths and potential failure modes.
Fiat-Backed Stablecoins
The simplest design: a company holds real-world assets in reserve and issues tokens that represent a claim on those assets. If you hold one token, the issuer promises it is redeemable for one dollar (or euro, or yen).
How they work
The issuer accepts deposits, keeps the cash (or cash-equivalent assets such as treasury bills) in a bank or custodian, and mints an equivalent number of tokens. When a holder redeems, tokens are burned and dollars are returned. The peg holds as long as users trust that the reserves are real and accessible.
Well-known examples include Tether (USDT) and USD Coin (USDC), two of the most widely traded assets in all of crypto — more liquid on many exchanges than most other tokens.
Strengths
- Simplicity. The mechanism is easy to understand: dollars in, tokens out.
- Capital efficiency. You deposit one dollar and get one dollar of stablecoin; no extra collateral required.
- Stability record. When reserves are genuine, fiat-backed stablecoins have maintained their pegs through severe market turmoil.
Failure modes
- Counterparty risk. If the issuer is insolvent, fraudulent, or has its bank accounts frozen, the reserves may not be there when you need them. This is a centralisation risk most other crypto assets do not carry.
- Opacity. Reserve auditing varies widely. Some issuers publish regular attestations from accounting firms; others have faced regulatory scrutiny over what exactly backs their tokens.
- Censorship. Central issuers can freeze or blacklist individual addresses, which conflicts with the ethos of permissionless finance.
Insight: A fiat-backed stablecoin is, at its core, an IOU issued on a blockchain. Its stability is only as good as the institution behind it — which makes due diligence on the issuer just as important as understanding the token itself.
Crypto-Backed Stablecoins
Instead of holding dollars in a bank, these stablecoins are backed by cryptocurrency locked in smart contracts on-chain. Because crypto prices are volatile, these systems require overcollateralization: you deposit more value than you borrow.
How they work
A user deposits collateral (often ETH or a basket of assets) into a smart contract and mints stablecoins worth less than the collateral value. If someone deposits $150 worth of ETH, they might mint $100 worth of stablecoins — a 150% collateralization ratio. If the collateral price drops toward the liquidation threshold, the protocol automatically sells the collateral to repay the stablecoin supply and protect solvency.
MakerDAO’s DAI is the canonical example. It is governed by token holders who vote on risk parameters like collateral types, debt ceilings, and liquidation ratios.
Strengths
- Transparency. Every unit of collateral is visible on-chain; anyone can verify the system’s health in real time.
- Decentralization. No single company controls the reserves; rules are enforced by code.
- Composability. These stablecoins plug natively into DeFi lending and borrowing protocols.
Failure modes
- Oracle risk. The smart contract needs an accurate, tamper-resistant price feed to know when to liquidate. If the price oracle is manipulated or fails, the system may undercollateralize before it can react. Oracles are a known vulnerability.
- Cascade liquidations. In a fast market crash, many positions may hit their liquidation thresholds simultaneously. The resulting wave of collateral sales pushes prices down further, triggering even more liquidations — a dangerous feedback loop.
- Capital inefficiency. Locking $150 to create $100 of stablecoins means capital is tied up and underused compared to fiat-backed models.
Algorithmic Stablecoins
Algorithmic stablecoins attempt to maintain a peg purely through software-driven supply adjustments, without holding an equivalent reserve in dollars or overcollateralized crypto. They are the most experimental category and have the most dramatic failure history.
How they work
There are several sub-designs, but the most common approach pairs the stablecoin with a second “governance” or “seigniorage” token. When the stablecoin trades above $1, the protocol mints more of it (diluting supply, pushing price down). When it trades below $1, users are incentivized to burn stablecoins in exchange for the companion token (reducing supply, pushing price up). The peg is maintained by arbitrage incentives rather than locked collateral.
Strengths
- Capital efficiency. No collateral needed; the system can scale supply without requiring deposits.
- Decentralization in principle. No reserves means no custodian to trust.
Failure modes
The history here is sobering.
| Event | What happened |
|---|---|
| TerraUSD (UST) collapse, 2022 | The algorithmic peg between UST and its companion token LUNA broke under selling pressure. As confidence fell, both tokens entered a “death spiral” — each collapse reinforcing the other. Tens of billions of dollars in value were destroyed in days. |
| Basis Cash, Empty Set Dollar | Earlier algorithmic experiments struggled to maintain pegs even under modest market stress, eventually losing them entirely. |
The fundamental problem is reflexivity: the mechanism that maintains the peg relies on confidence in the companion token, but confidence in that token depends on the peg holding. Under extreme pressure, both can collapse together. Unlike fiat-backed or crypto-backed models, there is no asset to liquidate and recover value from.
Pure algorithmic stablecoins are now widely considered among the highest-risk instruments in crypto — a cautionary example of how a technically elegant design can carry catastrophic systemic fragility.
Hybrid Models
The boundaries between categories are not always sharp. Some newer designs blend overcollateralization with algorithmic supply mechanisms, aiming to capture capital efficiency while retaining a collateral backstop. These “fractional-algorithmic” models are still being battle-tested and carry their own untested risk profiles.
Understanding which category a stablecoin falls into — and verifying the claims made about its reserves or code — is essential groundwork before using any stablecoin in a meaningful way. The tokenomics of a stablecoin’s companion assets, if it has them, deserve just as much scrutiny as the stablecoin itself.
Key Takeaways
- Fiat-backed stablecoins are simple and battle-tested but introduce counterparty and censorship risk through their reliance on centralized issuers.
- Crypto-backed stablecoins are transparent and on-chain but require overcollateralization and are vulnerable to oracle failures and cascade liquidations.
- Algorithmic stablecoins attempt to hold a peg through incentives alone; their history includes catastrophic failures, most notably the TerraUSD collapse in 2022.
- No stablecoin design is risk-free — the risks differ in type, not absence.
- Before using a stablecoin, identify who controls the reserves (or whether any exist), where you can verify them, and what happens to your funds if the mechanism breaks.
Next up: Wrapped Tokens