What is a stablecoin? The crypto built to sit still
USDT and USDC hold one dollar by design. How reserves keep the peg, how Terra UST lost 40 billion, what stablecoins are good for, and whether savings belong in one.
A stablecoin is a cryptocurrency built to hold one price, almost always one US dollar. Where Bitcoin swings, a stablecoin is engineered to sit still. That sounds boring, and it is the most used product in crypto. Stablecoins move more value in a day than most coins move in a month, because traders park money in them, savers in collapsing currencies flee to them, and workers send them across borders faster and cheaper than a wire transfer.
The two giants are Tether, written USDT, and USD Coin, written USDC. Together they account for hundreds of billions in circulation, riding on networks like Ethereum and Tron.
How does a stablecoin stay at one dollar?
The honest ones hold reserves. For every coin issued, the company keeps about a dollar of cash and short-term US government debt in accounts, and it stands ready to redeem coins for dollars. As long as redemption works, arbitrage traders keep the market price pinned near a dollar: if the coin dips to 99 cents, they buy it and redeem for a full dollar until the gap closes.
The catch is the word trust. You are trusting that the reserves exist, are liquid, and are where the company says. Tether paid fines in 2021 over past misstatements about its backing and has since published attestations, and skeptics have never fully relaxed. USDC publishes monthly reserve reports and is treated as the conservative choice. Neither is a government-insured bank account, and both can freeze addresses when law enforcement asks, which surprises people who thought crypto could not be frozen.
What happened with Terra and UST?
The cautionary tale of the whole category. UST was an algorithmic stablecoin, holding no real reserves. It kept its dollar peg through a mint-and-burn dance with a sister token called LUNA, and it paid savers near 20 percent interest, which should have been the first alarm. In May 2022 confidence cracked, the peg slipped, and the mechanism that was supposed to restore it instead printed LUNA into oblivion. Around 40 billion dollars of value evaporated in a week. Retirees and first-time investors were in it because 20 percent on a stable dollar sounded safe.
The lesson is not that stablecoins are doomed. It is that stable is a claim about the design, and designs differ. Reserve-backed and boring survived. Algorithmic and generous did not.
What are stablecoins actually good for?
Moving dollars like email. A remittance that costs a chunk of a paycheck through a wire service can cost cents as USDC on a cheap network and arrive in minutes. In countries with high inflation, people hold savings in stablecoins because a digital dollar beats a melting local note. Traders use them to step out of volatile coins without leaving crypto. And increasingly, ordinary payment companies settle transactions with them behind the scenes.
Governments noticed. The US passed stablecoin legislation in 2025 setting reserve and audit rules, and Europe's MiCA framework did similar work earlier. Regulation is turning the honest end of the category into something close to a licensed money service.
Should I keep savings in a stablecoin?
For most people with access to a solid bank, no advantage justifies the extra moving parts. A bank account has deposit insurance. A stablecoin has a company's balance sheet and your own wallet security, and a mistyped address or a drained wallet has no fraud department. Where stablecoins shine is movement and escape: crossing borders, leaving a collapsing currency, or settling fast. If you do hold them, prefer the transparent issuers, skip anything offering miracle interest, and remember Terra whenever a stable asset promises to also make you rich.