Crypto markets are known for wild price swings. Bitcoin can gain or lose thousands of dollars in value within a single day. That volatility is exciting for traders but deeply impractical for anyone trying to use digital money to, say, pay a bill, send a salary, or hold savings. This is the problem stablecoins were built to solve.
A stablecoin is a type of cryptocurrency designed to maintain a steady value — most commonly pegged to a traditional currency like the US dollar. One stablecoin unit aims to always be worth one dollar, or as close to it as possible. The stability comes not from magic, but from specific mechanisms that each design uses to hold the peg. Those mechanisms split the stablecoin world into three broad categories: fiat-backed, crypto-backed, and algorithmic.
**Fiat-Backed Stablecoins**
The simplest concept to grasp is the fiat-backed stablecoin. A company issues tokens on a blockchain and promises to hold an equivalent amount of real-world money — typically US dollars — in reserve. For every token in circulation, one dollar is supposed to sit in a bank account or be held in similarly safe, liquid assets.
USDT (Tether) and USDC (USD Coin) are the largest examples. When you hold one USDT, you are trusting that the issuer has a real dollar backing it. To redeem, you return the token and receive the underlying currency.
The appeal is simplicity and reliability. Fiat-backed stablecoins have the strongest track records for holding their pegs under normal market conditions. The tradeoff is that they reintroduce the very thing crypto was meant to reduce: reliance on centralized institutions. You must trust the company to actually hold the reserves they claim, submit to audits, and not freeze or block your funds. Regulatory scrutiny of these issuers has increased steadily as the market has grown.
**Crypto-Backed Stablecoins**
Crypto-backed stablecoins take a different approach. Instead of holding dollars in a bank, they are backed by other cryptocurrencies — typically locked up in smart contracts on a blockchain. Because crypto is itself volatile, these systems require users to post significantly more collateral than the stablecoins they receive. This overcollateralization acts as a buffer against price swings.
DAI, issued by the MakerDAO protocol, is the most established example. To mint DAI, a user locks up Ethereum or other accepted assets worth more than the DAI they want to create. If the value of that collateral drops too far, the system automatically liquidates it to protect the peg.
The advantage here is decentralization. There is no company holding dollars in a bank account and no single entity that can freeze your funds. The rules are enforced by code. The risk, however, is that extreme and rapid market downturns can outpace the system's ability to liquidate collateral, potentially causing the stablecoin to lose its peg. These systems are also more complex and harder for the average user to understand.
**Algorithmic Stablecoins**
Algorithmic stablecoins are the most experimental and, historically, the most dangerous category. They attempt to hold a peg not through held assets but through automated supply and demand mechanics — expanding the supply of tokens when the price rises above the peg and contracting it when the price falls below.
Some designs use a two-token model: one token serves as the stablecoin, and a second token absorbs volatility and provides the economic incentive to keep the system balanced. In theory, arbitrage traders profit by correcting the peg whenever it drifts. In practice, if confidence in the system collapses, the mechanism can go into reverse — a "death spiral" where falling prices trigger more selling, which drives prices lower still.
The 2022 collapse of TerraUSD (UST) and its sister token LUNA remains the most dramatic example of this failure mode. Billions of dollars in value were wiped out in days when the algorithmic peg broke down irreparably. The event sent shockwaves through the broader crypto market and drew significant regulatory attention worldwide.
Some newer designs attempt hybrid models — combining partial collateral with algorithmic elements — in an effort to get the best of both worlds, though these remain largely unproven at scale.
**Why This Matters**
Stablecoins are no longer a niche corner of crypto. They are core infrastructure for decentralized finance, a common tool for moving money across borders, and increasingly a subject of legislation in major economies. Understanding what backs a stablecoin — and what can go wrong — is essential context for anyone navigating the space.
The fundamental question for any stablecoin is always the same: what guarantee holds the peg, and how robust is that guarantee under stress? Fiat-backed coins answer with audited reserves and institutional trust. Crypto-backed coins answer with transparent, on-chain collateral and code. Algorithmic coins answer with economic incentives — which, as history has shown, can evaporate quickly.
None of these approaches is perfect. Each involves tradeoffs between decentralization, stability, and scalability. Knowing which type of stablecoin you are using — and what assumptions underpin it — is simply good practice.