Stablecoins are cryptoassets designed to hold a steady value—usually $1—so people can move money on blockchains without the dizzying volatility of typical cryptocurrencies. They’ve become the dominant “transaction rail” of crypto trading and DeFi lending, and increasingly a building block for cross-border payments. Policymakers are catching up fast: the U.S. just enacted the GENIUS Act, the EU has MiCA in force, and the UK and others are finalizing their own rules. U.S. Department of the TreasuryCongress.govesma.europa.euFCA

What exactly is a stablecoin?

A stablecoin is a digital token whose value is pegged to something stable (usually a fiat currency like the U.S. dollar). Several designs exist, each with its own trade-offs in transparency, resilience, and scalability. Policymakers and central-bank researchers usually group them into four buckets: fiat-backed (aka “cash-and-T-bills”), commodity-backed, crypto-collateralized, and algorithmic. InvestopediaBank for International SettlementsFederal Reserve

1) Fiat-backed (cash & Treasuries)

These tokens (for example, USDC or USDT) are issued by a company that promises to hold reserves—cash, central-bank deposits, or short-dated U.S. Treasuries—equal to 100% of outstanding tokens. The token should be redeemable at par ($1) on demand, subject to the issuer’s terms. The appeal is simplicity and (ideally) verifiable reserves, but users rely on the issuer, custodians, and auditors. IMF

2) Commodity-backed

Instead of dollars, the peg references a commodity such as gold (e.g., tokens redeemable for specified gold bars). These inherit the commodity’s market dynamics and custody complexities. They’re a small slice of the market but fit the same logic as fiat-backed coins: every token should map to inventory held with a qualified custodian. Investopedia

3) Crypto-collateralized (over-collateralized)

Protocols like MakerDAO allow users to lock crypto (e.g., ETH) in a smart contract vault and mint a dollar-pegged token (DAI). Because collateral is volatile, the system requires excess collateralization—often 150% or more—and liquidates collateral if the position’s “health factor” falls too low. This is transparent and on-chain, but depends on oracle reliability, liquidation mechanics, and market liquidity. makerdao.comBank for International Settlements

4) Algorithmic (unbacked)

These attempt to keep $1 without holding reserve assets, using mint/burn rules or a second “volatility-absorbing” token to push the price back to the peg. History shows they are fragile under stress because they rely on market confidence and arbitrage working perfectly—even in a panic. Federal ReserveBank for International Settlements

Reality check. Across designs, stability is a goal, not a guarantee. Central-bank research finds many stablecoins deviate from par during stress, and even well-backed coins can wobble when counterparties or banks in their reserve chain are in trouble. ReutersBank for International Settlements

Why stablecoins matter

The U.S. GENIUS Act: what changed in 2025

In July 2025, the United States enacted the Guiding and Establishing National Innovation for U.S. Stablecoins Act (GENIUS Act)—the country’s first comprehensive federal law for payment stablecoins (i.e., dollar-pegged tokens meant for payments, not investment). It creates licensing paths, prudential standards, and clear supervisory lines for issuers. Congress.govSidley Austin

Who can issue a U.S. payment stablecoin?

It’s unlawful for anyone other than a permitted payment stablecoin issuer to issue a payment stablecoin in the U.S. That includes banks and credit-union affiliates, plus newly licensed nonbank issuers. Foreign issuers may participate if they meet “comparable” standards. Oversight of federally licensed nonbank issuers sits with the Office of the Comptroller of the Currency (OCC). Congress.govLatham & WatkinsOCC.gov

Core prudential rules

Timing

Much of GENIUS becomes effective the earlier of 18 months after enactment or 120 days after the regulators finalize implementing rules. Agencies have a one-year rule-making push and are coordinating on detailed liquidity, custody, and risk-management standards. Latham & WatkinsGibson Dunn

Big picture: The law is intended to corral stablecoin risks without choking innovation—bringing issuers into a bank-like perimeter (for prudential safeguards) while keeping tokens usable across crypto apps and payment flows. WilmerHale

Outside the U.S.: MiCA and other regimes

These frameworks broadly rhyme: 1:1 reserve standards, segregated assets, strong disclosures, and authorization/supervision of issuers and key service providers.

How stablecoins power DeFi

DeFi lending markets use stablecoins as both collateral and borrowable assets. The mechanics are transparent but unforgiving—everything is enforced by code.

Using stablecoins to borrow against assets

  1. Supply volatile collateral. On protocols like Aave, you deposit assets (e.g., ETH) into a pool and enable them as collateral. Your account gets a “health factor” that must remain above a threshold. aave.com+1
  2. Borrow a stablecoin. You borrow USDC/DAI against that collateral, typically well below its value. If prices fall and your health factor drops too low, your collateral can be liquidated to repay the loan. CoinMarketCap
  3. Over-collateralization is the rule. DeFi lending is rarely under-collateralized; common loan-to-value caps keep the system solvent through volatility. Bank for International Settlements
  4. Risk controls. Aave’s “siloed/isolated” markets constrain which assets can be borrowed against riskier collateral, limiting contagion. aave.com+1

Minting a decentralized stablecoin (DAI)

With MakerDAO, users lock collateral in a vault and mint DAI up to a set ratio (often 150%+). If the vault’s collateral value falls below the required ratio, the protocol auctions collateral to keep DAI solvent. This is transparent but depends on sound oracles and liquid markets during shocks. makerdao.com

Where “yield” comes from (and why it changes)

Stablecoin “yield” isn’t paid by compliant payment-coin issuers under GENIUS; it comes from how tokens are deployed:

Why yields move: In crypto “credit cycles,” borrowing demand can evaporate quickly in risk-off periods, compressing rates; during bull markets the opposite occurs. Shock events (like a de-pegging scare) can also distort rates and liquidity. ScienceDirectSSRN

Risk checklist (for both retail and institutions)

  1. Issuer & reserve risk (fiat-backed coins). Demand regular, independent attestations, clear redemption terms, and details on reserve composition, custody, and concentration. The GENIUS Act forces monthly reporting and audits—use them. Congress.gov
  2. Smart-contract & oracle risk (DeFi). Even audited code can fail; consider bug-bounty history, time in market, and oracle design.
  3. Liquidation risk. Over-collateralized loans can be liquidated fast if prices gap; monitor health factors and set conservative buffers. Bank for International Settlements
  4. De-peg risk. Every design can wobble around $1; algorithmic coins are the most fragile, but fiat-backed coins can also drift under stress. Bank for International Settlements
  5. Legal & compliance scope. Under GENIUS, U.S. issuers must meet BSA/AML obligations; MiCA sets EU-wide authorization and disclosure rules. Cross-border users should check which regime applies to them. The White Houseesma.europa.eu

Practical ways to use stablecoins safely in DeFi

How GENIUS interacts with DeFi

GENIUS regulates issuers and the tokens they mint—not DeFi protocols per se. But it will still shape DeFi:

Closing thought

Stablecoins started as crypto’s workaround for volatility; they’re now becoming a regulated payments instrument with global ambitions. The GENIUS Act in the U.S. and MiCA in Europe move the conversation from “Should stablecoins exist?” to “How do we make them safe, auditable, and useful?” For users, the playbook is straightforward: understand the design you’re holding, read the issuer’s disclosures, and treat DeFi yields like any other form of variable credit income—earned by taking risk, not found money.