What are stablecoins? USDT, USDC, and the depeg risk you should know
How stablecoins peg to the USD, the difference between USDT and USDC, asset-backed vs algorithmic types, and depeg risk through the Luna/UST lesson.
Nearly every crypto trade passes through a stablecoin. You buy BTC with USDT, earn yield in USDC, park "safe" money in stablecoins when the market drops. But "stable" doesn't mean "risk-free."
This post explains how stablecoins work, how they differ, and the depeg risk you need to understand before holding large amounts.
What is a stablecoin?
Stablecoin = a crypto token designed to hold a stable value, usually pegged 1:1 to an asset — most commonly the US dollar (USD).
The goal: 1 USDT ≈ 1 USD, always. This lets you hold value as "digital dollars" on a blockchain without BTC-level volatility, while transacting fast without going through a bank.
Why stablecoins matter
- Bridge between fiat and crypto: deposit into USDT/USDC, then use it to buy other assets.
- Safe haven when markets drop: sell BTC into USDT to "go to cash" without leaving the exchange.
- Common unit of account: most trading pairs (BTC/USDT, ETH/USDT) are quoted in stablecoins.
- Payments and transfers: send USDT across borders in minutes, low fees.
Types of stablecoins
1. Fiat-backed
Each token is backed by real cash or short-term bonds held at a bank/institution. This is the safest type if the reserves are transparent.
- USDT (Tether): the largest, most liquid, most widely used. Has faced criticism over reserve transparency.
- USDC (Circle): considered more transparent, audited regularly, preferred by institutions.
2. Crypto-backed
Backed by other crypto assets, usually over-collateralized to withstand volatility. Example: DAI.
3. Algorithmic
No real backing asset — they use an algorithm and a companion token to maintain the peg. This is the highest-risk type. Famous failure: UST (Terra/Luna).
What is a depeg — and the Luna/UST lesson
Depeg = a stablecoin loses its peg, drifting away from 1 USD.
In May 2022, UST — an algorithmic stablecoin — lost its peg and collapsed from 1 USD toward zero in days, dragging the Luna token down about 99%. Tens of billions of dollars evaporated.
Root cause: UST had no real backing, relying only on a "mint/burn" mechanism with Luna. When confidence broke, the sell-off spiral made the mechanism self-destruct.
Even backed stablecoins have briefly depegged: in March 2023, USDC dropped to about 0.87 USD when part of its reserves was stuck at the failed SVB bank — then recovered to 1 USD once the situation cleared.
The lesson: no stablecoin is absolutely safe. Real-backed, transparent ones carry less risk than algorithmic ones.
How to reduce risk when holding stablecoins
- Prefer transparent, large-cap coins (USDT, USDC) over small, obscure stablecoins.
- Avoid algorithmic stablecoins entirely if you don't understand the mechanism — unusually high yields often come with depeg risk.
- Spread out if holding large amounts — don't put everything in one coin.
- Be wary of high yields: anyone promising 20%/year on a stablecoin is taking risk somewhere — see Crypto lending risks.
Stablecoins in a DCA strategy
When DCA-ing crypto, the stablecoin is what you buy with. fastbot uses USDT as the buy unit on Binance (via quoteOrderQty) — you deposit USDT and the bot buys the target coin on schedule.
Practical note: holding stablecoins while waiting to DCA is normal, but don't hold too much for too long out of fear — that's market-timing in disguise. See What is DCA.
Conclusion
Stablecoins are essential crypto infrastructure — convenient, fast, the common unit of account. But "stable" does not mean "absolutely safe."
Simple rule: use large, transparent stablecoins; avoid algorithmic ones; be skeptical of unusually high yields; and don't keep all your assets in a single coin.
Next step
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