Stablecoins (the most-used product in crypto)

The category that has quietly won

Stablecoins are the most-used product in crypto by a wide margin. The number of dollars settled through stablecoin transactions per month exceeds PayPal's monthly volume and is approaching Visa's. In several emerging markets, more dollars now flow through stablecoins than through correspondent banking. This category has, without much fanfare, already won.

What most users do not appreciate is that "stablecoin" is not one product. It is a category that contains three structurally different designs, each with its own failure modes. Treating all stablecoins as interchangeable is the single most common mistake people make in this space, and it is the mistake that has cost them the most money. Understanding the categories is the prerequisite for using stablecoins safely.

What a stablecoin actually is

A stablecoin is a cryptocurrency designed to maintain a stable price, typically pegged to one US dollar. The peg is the entire product. A stablecoin that does not stay at one dollar is a failed stablecoin, regardless of how interesting its design is or how well it functions for a while.

Stablecoins exist because volatility makes most cryptocurrencies impractical for everyday use. You cannot pay someone five bitcoin for rent if bitcoin moves twenty percent in a week. You can pay someone 5,000 USDC for rent and the receiver knows what they are getting. This separation of functions — Bitcoin and other volatile crypto assets as a store of value, stablecoins as the medium of exchange — has settled into place across the crypto economy.

The three categories below differ in how they maintain their peg. The differences are not academic. They determine which category survives stress.

Fiat-backed stablecoins

This is the largest category by far. Tether's USDT and Circle's USDC together account for over ninety percent of all stablecoin supply in circulation.

The mechanism is simple. The issuer holds one dollar in reserve for every stablecoin issued. When you deposit a dollar, you get one stablecoin. When you redeem a stablecoin, you get one dollar back. The reserves are usually held in some combination of cash, short-term US Treasury bills, and money market instruments.

Circle publishes monthly attestations of its USDC reserves by a third-party accounting firm. Tether has historically been less transparent but has improved its reporting since 2021 and now publishes quarterly attestations.

The structural risk is that you are trusting the issuer. Not the blockchain. Not the protocol. The company that says they are holding the reserves. If the company misrepresents its reserves, holds them in inappropriate assets, becomes insolvent, or is shut down by regulators, the stablecoin can lose its peg. USDC depegged briefly in March 2023 when some of its reserves were stuck in the failing Silicon Valley Bank. Tether has wobbled at various stress points throughout its history.

For day-to-day use, fiat-backed stablecoins from major issuers are reliable enough that the peg is not a meaningful concern. For holding meaningful balances long-term, the question is which issuer you trust and how diversified you are if one issuer fails.

Crypto-backed stablecoins

Crypto-backed stablecoins are decentralized. They do not have a company issuing them. Instead, they are minted by smart contracts that hold cryptocurrency collateral.

The flagship example is DAI, issued by MakerDAO (now part of the Sky ecosystem). To mint DAI, you deposit cryptocurrency — typically ETH or other approved tokens — into a Maker smart contract. The contract issues DAI against your collateral, with a required over-collateralization ratio of one hundred fifty percent or higher. Deposit $150 of ETH, you can mint up to $100 of DAI. If the value of your ETH falls below the threshold, the smart contract automatically liquidates the position to ensure DAI remains fully backed.

This system has been operating since 2017 and has weathered every major crypto market drawdown without breaking. The DAI peg has held within reasonable bounds across cycles where centralized stablecoins have wobbled.

The tradeoff is capital inefficiency. Holding $150 of crypto to mint $100 of stablecoin is not how most users want to interact with the dollar. Crypto-backed stablecoins are valuable specifically when decentralization matters more than capital efficiency — when the user does not want to trust an issuer that could be pressured by regulators or could go insolvent. For most use cases this is unnecessary. For specific use cases — long-term holding, fully decentralized DeFi positions, jurisdictions with hostile regulatory regimes — it is the right design.

Algorithmic stablecoins

This category exists primarily as a cautionary tale.

Algorithmic stablecoins attempt to maintain their peg through algorithmic and incentive mechanisms rather than collateral. They are typically under-collateralized or uncollateralized entirely. The system creates supply and demand pressures through linked-token mechanisms designed to keep the price stable.

The category's collapse was definitive. In May 2022, TerraUSD (UST), an algorithmic stablecoin that had reached over $18 billion in circulation, lost its peg over the course of a few days and went to near-zero. The collapse wiped out roughly $40 billion of value across the broader Terra ecosystem and contributed to a chain of failures that took down Three Arrows Capital, Celsius, Voyager, and several other firms.

The structural problem is that algorithmic stablecoins depend on continuous demand for the linked token to maintain the peg. If demand falters below a critical threshold, the algorithm cannot defend the peg. The reflexive dynamics that maintain stability in good conditions accelerate the collapse in bad conditions. The 2022 Terra collapse was not a black swan. It was the predictable outcome of a design that worked until it didn't, and when it didn't, it failed catastrophically.

Smaller algorithmic stablecoins have continued to be launched and continued to fail. As a category, algorithmic stablecoins should be considered structurally untrusted until a new generation of designs proves otherwise across multiple stress cycles. None has yet.

How to choose which stablecoin to use

For practical purposes, most people will use fiat-backed stablecoins — USDC or USDT — for most things. Both are widely accepted across decentralized exchanges, lending protocols, and centralized exchanges. The differences for typical use are minor.

Some considerations that might shift the choice:

Regulatory exposure. USDC is issued by a US-regulated entity (Circle) and holds reserves at US banks. USDT has historically been more regulatory-distant. For users worried about US regulatory pressure, USDT has been more resilient. For users worried about banking-system stress, USDC's transparency is preferable.

Geographic concentration. USDT dominates in emerging markets, Asian crypto trading, and TRON-network usage. USDC dominates in US institutional and Ethereum-DeFi contexts.

Decentralization preference. For users who want to minimize trust in any centralized issuer, DAI remains the most credible decentralized option, though smaller than USDC or USDT.

The practical takeaway

Use fiat-backed stablecoins for everyday on-chain dollar use. The risk is issuer-level, not protocol-level. The biggest US-regulated issuer is Circle (USDC); the largest globally is Tether (USDT). For most purposes either is fine.

Use crypto-backed stablecoins when decentralization matters more than capital efficiency. DAI is the most-tested option in this category.

Treat algorithmic stablecoins as structurally suspicious until a new design proves itself. The 2022 Terra collapse should be your default assumption for the category, not an exception.

Diversify across issuers if you hold meaningful balances. The cost is near-zero. The protection if one issuer fails is meaningful.

The next module looks at where you actually trade these stablecoins (and everything else). Centralized exchanges, decentralized exchanges, and the structural differences that determine which one is right for what.