Stablecoins exist to solve a specific problem: most useful crypto activity — trading, lending, paying for something — is much easier when at least one side of the transaction isn't swinging in value by double-digit percentages in a day. A stablecoin is designed to hold a stable value, usually pegged to a major currency like the US dollar, while still moving on a blockchain with the speed and programmability that entails.

The word "stable" describes a goal, not a guarantee. How that goal is pursued differs enormously between issuers, and the differences matter far more than the shared "stablecoin" label suggests.

Three mechanisms, three different bets

Fiat-collateralized

The issuer holds reserves — cash, short-term government debt, and similar low-risk assets — roughly equal in value to the tokens in circulation, typically held with regulated custodians. When you redeem the token, the issuer sends you the underlying dollars and removes the token from circulation. This is conceptually the simplest model, and it's the dominant one by market share.

The bet here isn't cryptographic — it's about trust in a company. Does the issuer actually hold what it claims? Is the reserve composition as low-risk as advertised? Can redemptions be honored quickly under stress? Because the assurance mechanism is usually periodic attestations or audits rather than fully continuous, public verification, fiat-collateralized stablecoins concentrate risk in the accuracy and honesty of that reporting.

Crypto-collateralized

Instead of holding dollars, the issuing protocol holds other crypto assets — often over-collateralized, meaning the value locked up exceeds the value of stablecoins issued against it, to absorb price swings in the collateral itself. If collateral value falls too close to the value of debt issued against it, the protocol automatically liquidates positions to protect the peg.

This model trades company-trust for smart-contract-and-market-trust: the code has to work correctly, and the collateral market has to stay liquid enough to liquidate positions without a death spiral, even during the kind of fast, broad crash where every collateral asset tends to fall at once.

Algorithmic

No full collateral backing at all — instead, the protocol uses incentives (minting and burning a second, floating-value token in response to price deviations) to try to hold the peg through market mechanics alone. This model has the least direct backing and, correspondingly, the worst track record: several prominent algorithmic stablecoins have lost their peg entirely and never recovered, because the mechanism depends on continued market confidence to function, and confidence is exactly what disappears first in a crisis.

"Stablecoin" describes a goal, not a risk level. A fiat-collateralized token backed by cash reserves, a crypto-collateralized token secured by a liquidation engine, and an algorithmic token held up mostly by market confidence are three very different risk profiles wearing the same label.

How pegs actually break

A peg doesn't need to reach zero to be considered broken — even a sustained deviation of a few cents from the target is treated as a serious event, because it signals the underlying mechanism is under real stress. Historically, breaks have come from a small number of repeating causes:

  1. 01

    Reserve doubt

    Questions about whether fiat-backed reserves are fully sufficient, sufficiently liquid, or held where claimed, triggering redemption pressure the issuer struggles to meet quickly.

  2. 02

    Collateral collapse

    A sharp fall in crypto-collateral value that outruns the protocol's ability to liquidate positions in an orderly way, especially during broad market crashes when liquidity for the collateral itself dries up.

  3. 03

    Confidence spirals

    For algorithmic designs specifically, a loss of confidence becomes self-fulfilling: as the peg wavers, the incentive to hold the token weakens, which weakens the peg further, in a loop that has repeatedly proven difficult to stop once started.

  4. 04

    Contagion from a connected failure

    Because stablecoins are deeply integrated into DeFi lending and trading, the failure of one connected protocol or exchange can create forced selling that pressures pegs across the system, even for tokens with no direct exposure to the original failure.

What to actually check

Before relying on a stablecoin for anything beyond small, short-term use, it's worth understanding a few basic facts about it:

  • Which collateral model it uses, and therefore which category of risk applies.
  • For fiat-backed tokens: how reserves are composed, how often they're attested, and by whom.
  • For crypto-collateralized tokens: the collateralization ratio and how the liquidation mechanism behaves under stress.
  • How deeply the token is integrated into the DeFi protocols you use — a stablecoin's failure tends to ripple into every lending market and trading pair built on top of it.

Why this matters beyond crypto-native trading

Stablecoins have increasingly become infrastructure — used for cross-border payments, as the base currency of DeFi lending, and as a dollar-denominated savings vehicle in places with less stable local currencies. That growing role is exactly why regulators have focused so heavily on reserve transparency: the more a stablecoin behaves like money people depend on, the more the consequences of a broken peg extend beyond the people who chose to hold it directly.