Stablecoins explained in plain English: they’re a type of cryptocurrency designed to hold a steady value — usually $1 — while still living on a blockchain. That sounds simple, but the how behind keeping a stablecoin at $1 varies wildly. And as millions of people learned in 2022, the difference between a well-designed stablecoin and a poorly designed one can cost you everything.
This guide covers the three main types, walks through the Terra/UST collapse as a real-world cautionary tale, and gives you a 3-question framework to evaluate any stablecoin before you use one.
What Is a Stablecoin and Why Does It Exist?
Regular cryptocurrencies like Bitcoin or Ethereum swing wildly in price — sometimes 10%, 20%, or more in a single day. That volatility makes them hard to use as money. If you’re trying to pay a freelancer in another country or park profits from a trade, you don’t want your payment to lose 15% of its value overnight.
Stablecoins solve that problem. They’re pegged (tied in value) to something stable, usually the US dollar, so 1 stablecoin = $1. They give you the portability and speed of crypto with the price stability of cash.
They’re also the main on-ramp to DeFi — short for decentralized finance, meaning financial apps that run on a blockchain without banks in the middle. If you want to earn yield on a DeFi platform or make a quick trade without converting back to dollars, stablecoins are the bridge.
But not all stablecoins are built the same way — and that’s where things get complicated.
How Stablecoins Work: Three Very Different Designs
Fiat-Backed: USDC vs USDT
These are the most straightforward. The idea: for every stablecoin in circulation, the issuer holds an equivalent dollar (or near-dollar asset) in reserve. You give them $100, they give you 100 stablecoins. When you want your dollars back, you swap back.
USDC (issued by Circle) and USDT (issued by Tether) are the two biggest fiat-backed stablecoins. Together they handle hundreds of billions of dollars in daily transaction volume.
The difference between USDC vs USDT comes down to transparency. USDC publishes monthly attestations from third-party auditing firms and holds reserves primarily in cash and short-term US Treasuries. USDT has faced long-running questions about what’s actually backing it — past disclosures revealed a mix of commercial paper, loans to affiliates, and other assets that aren’t quite “cash in a bank account.”
Fiat-backed stablecoins are generally the most stable type, but they come with counterparty risk: you’re trusting a company. If that company gets hacked, goes bankrupt, or runs into regulatory trouble, your stablecoin could be affected.
Crypto-Backed: DAI
DAI (issued by MakerDAO) takes a different approach: it’s backed by other cryptocurrencies, primarily ETH (Ethereum). The key mechanic is overcollateralization — to mint $100 worth of DAI, you have to lock up significantly more than $100 worth of ETH as collateral.
Why? Because ETH’s price moves. The extra buffer protects DAI’s $1 peg even when collateral values drop. If your collateral falls too far, the system automatically liquidates it to protect the peg.
The upside: DAI is more decentralized and transparent — everything runs on-chain via smart contracts (self-executing code on the blockchain). The downside: it’s more complex, and if crypto markets crash hard and fast, even a large collateral buffer can be strained.
Algorithmic Stablecoins: When There’s No Vault
Algorithmic stablecoins try to maintain their $1 peg through code and economic incentives rather than held assets. There’s no vault of dollars. Instead, an algorithm adjusts supply based on demand — minting more tokens when price rises above $1, burning tokens when it falls below.
The theory sounds elegant. The practice, as the world saw in May 2022, can be catastrophic.
The Terra/UST Collapse: A $40 Billion Warning
Terra’s UST was an algorithmic stablecoin that grew explosively through 2021 and early 2022. At its peak, UST had a market cap above $18 billion. Terra’s flagship platform, Anchor Protocol, promised 20% annual yield on UST deposits — a number that attracted enormous inflows from retail investors who saw it as “stable” savings with great returns.
The mechanism: UST was linked to a sister token called LUNA. You could always swap $1 worth of LUNA for 1 UST, and vice versa. This arbitrage loop was supposed to keep UST at $1.
When large holders began selling UST in May 2022, the peg wobbled. Arbitrageurs were supposed to profit by buying cheap UST and burning it for LUNA — but the selling pressure came too fast and too large. The system couldn’t absorb it. As UST fell below $1, panic selling accelerated. Vast quantities of LUNA were minted to try to defend the peg, flooding the market and crashing LUNA’s own price. With LUNA worth nearly nothing, there was nothing left to defend UST with.
UST fell from $1 to near zero in a matter of days. LUNA, once trading above $80, collapsed to fractions of a cent. Billions of dollars in ordinary people’s savings were wiped out.
The warning signs that existed beforehand — and that most people ignored:
- A 20% annual yield with no clear, sustainable source (real yield has to come from somewhere)
- No hard assets backing the peg — only a circular mechanism between two related tokens
- Heavy concentration of UST in a single platform (Anchor), meaning one point of failure held most of the risk
- The project’s own emergency reserve (Luna Foundation Guard) was deployed and depleted trying to defend the peg — and still failed
Algorithmic stablecoins have a fundamental design problem: they work when confidence is high and can collapse instantly when confidence falters. No reserve means no floor.
Stablecoins Explained: A 3-Question Framework Before You Use One
Before using any stablecoin — whether in a DeFi protocol, for a transfer, or to park funds — ask these three questions:
1. What backs it, and is that backing audited?
Is there a third-party audit or attestation of the reserves? For fiat-backed coins, look for monthly reserve reports from a credible accounting firm. If the issuer doesn’t publish this, treat that as a yellow flag. If the “backing” is another volatile token or a pure algorithm, treat that as a serious risk.
2. Who issues it, and are they regulated?
Circle (USDC) operates under US regulatory frameworks and publishes transparency reports. Tether (USDT) has had a more turbulent regulatory history but remains dominant by volume. Unknown or offshore issuers with no oversight carry more risk. Regulated doesn’t automatically mean safe — but it does mean more accountability when things go wrong.
3. Is it overcollateralized, or does it depend on confidence alone?
Overcollateralized means there are more assets backing the stablecoin than stablecoins in circulation — a real buffer exists. Ask: if half the users wanted out tomorrow, would the peg hold? With fiat-backed coins and DAI, the answer is likely yes. With pure algorithmic designs, the answer is “it depends on nobody panicking.” That’s not a safe answer.
Practical Uses for Stablecoins
Once you understand the risks, stablecoins have real, everyday uses:
- DeFi entry point: Most DeFi protocols accept USDC or DAI. Converting dollars to stablecoin is often the first step into decentralized finance.
- Cross-border transfers: Sending $500 internationally via stablecoin often costs pennies and settles in minutes, versus wire transfer fees and multi-day waits through traditional banks.
- Earning yield: DeFi lending platforms let you earn interest on stablecoins — though that yield comes with its own risks, including smart contract bugs and platform failures.
Before you move stablecoins into any DeFi app, understanding what wallet permissions you’re granting those protocols is critical. What looks like a simple “connect wallet” step often involves signing approvals that give a smart contract significant access to your funds — something we’ll cover in depth in our upcoming guide on wallet permissions and DeFi approvals.
And before any of this — you need a secure wallet to hold your stablecoins. A wallet you actually control, not an exchange account where the exchange holds your private keys.
The Bottom Line
Stablecoins explained in three sentences: they’re crypto designed to hold $1, they do that through three very different mechanisms, and the safest ones have real assets behind them that you can verify. The 3-question framework — What backs it? Who issues it? Is it overcollateralized? — gives you a fast way to assess any stablecoin before you put money in.
Don’t skip that assessment. Terra/UST taught us that “stable” in the name doesn’t make something safe.
Before you use stablecoins, you need a secure place to hold them. Download Wallet Security: Your Complete Setup Guide — a free, step-by-step walkthrough for setting up a crypto wallet you actually control. No jargon, no upsells.