A stablecoin is a cryptocurrency designed to hold a steady value by being pegged to a stable reference asset — almost always the US dollar. One unit of a dollar-pegged stablecoin like USDC or USDT is meant to always be worth about $1. This gives you the speed, programmability, and self-custody of crypto without the wild price swings of assets like BTC or ETH, which is why stablecoins have become the default unit of account and trading collateral across crypto.
Why Stablecoins Exist
Most cryptocurrencies are volatile. That's fine for speculation, but it's a problem when you need a stable place to park value, settle trades, or measure profit and loss. Before stablecoins, moving "to cash" inside crypto meant selling back to fiat through a bank — slow and clunky.
A stablecoin solves this by keeping a steady value while living entirely onchain. You can hold it in your own crypto wallet, send it anywhere in minutes, and use it as a dollar-equivalent without leaving the crypto ecosystem. It's the bridge between volatile assets and a stable store of value.
Types of Stablecoins
Not all stablecoins maintain their peg the same way. The main categories:
- Fiat-backed (collateralized). The most common type. Each token is backed by reserves — dollars, cash equivalents, and short-term treasuries — held by the issuer. USDC and USDT are the leading examples. You trust the issuer to hold real reserves redeemable 1:1.
- Crypto-backed. Backed by a surplus of other crypto assets locked in smart contracts, over-collateralized to absorb volatility. These are more decentralized but rely on the value of their crypto collateral holding up.
- Algorithmic. Attempt to hold the peg through supply-and-demand algorithms rather than reserves. These have historically been the riskiest, and several have failed dramatically when confidence collapsed and the peg broke.
For most traders, fiat-backed stablecoins like USDC and USDT are the practical default because they're widely supported and deeply liquid.
How the Peg Is Maintained
A fiat-backed stablecoin holds its peg through redeemability and arbitrage. If reserves genuinely back each token 1:1, then:
- If the price drifts below $1, arbitrageurs buy the discounted token and redeem it for a full dollar, profiting and pushing the price back up.
- If the price drifts above $1, more tokens are minted and sold, pushing it back down.
The peg is only as strong as confidence in the reserves behind it. A "depeg" happens when the market doubts those reserves or redemption breaks down — which is why the quality and transparency of an issuer's backing matters.
Stablecoins as Trading Collateral
This is where stablecoins matter most for traders. On crypto trading platforms, stablecoins are the standard collateral and settlement asset.
- Margin and collateral. When you trade perpetual futures, your margin is typically denominated in a stablecoin. Your gains and losses settle in it too, so your account value is measured in stable dollar terms rather than a fluctuating asset.
- A stable home base. Between trades, holding stablecoins lets you sit in "cash" without exiting crypto. You're ready to deploy instantly when an opportunity appears.
- Clear PnL. Because the unit of account is dollar-stable, your profit and loss is easy to read — a $100 gain is $100, not "0.03 ETH that might be worth more or less tomorrow."
Using a stablecoin as collateral means the only thing moving your account value is your trading performance, not the currency you're collateralized in. Start trading on Legend to use stablecoin collateral across perps on crypto, stocks, and commodities from one self-custody account.
A Few Things to Keep in Mind
- Issuer risk is real. Fiat-backed stablecoins depend on the issuer actually holding the reserves. Stick to established, transparent issuers.
- Depegs happen. Even major stablecoins have briefly traded off-peg during stress. They usually recover, but it's a reminder that "stable" isn't "risk-free."
- It's still self-custody. Holding stablecoins in your own wallet means you control them — and you're responsible for your keys.
- Onchain transfers cost network fees. Moving stablecoins incurs gas fees, just like any onchain transaction.
Stablecoins are the connective tissue of crypto trading: a stable, onchain dollar you can hold, move, and trade against. Whether you're on a centralized venue or comparing a CEX vs a DEX, they're how value sits still while you decide what to do next.