Stablecoins settled more than $10.8 trillion in on-chain transactions during 2024, surpassing Visa’s annual payment volume for the first time. Yet every stablecoin in circulation relies on one of just three mechanical designs to hold its value at $1. Some back each token with dollars in a bank vault. Others lock up cryptocurrency worth far more than the tokens they issue. A third category tried to use algorithms alone, and the most prominent example erased $45 billion in a week. This is how stablecoins actually work, from the reserve accounts to the smart contracts to the regulatory frameworks now reshaping the market.
Key Takeaways
- Fiat-backed stablecoins like USDT and USDC hold reserves in cash, Treasury bills, and money market funds to guarantee 1:1 redemption.
- Crypto-collateralized stablecoins like DAI require users to lock up 150% or more in cryptocurrency collateral, with automatic liquidation if values drop.
- Algorithmic stablecoins use code to expand and contract token supply, but the TerraUST collapse in May 2022 proved this model is fundamentally fragile under market stress.
- The stablecoin market reached approximately $235 billion in total capitalization by early 2026, with USDT holding roughly 62% market share.
- The EU’s MiCA regulation (effective December 2024) and the proposed US GENIUS Act are creating the first formal licensing and reserve requirements for stablecoin issuers.
- Every peg mechanism depends on arbitrage incentives, meaning the $1 value holds only as long as traders can profitably correct deviations.
What Are Stablecoins?
A stablecoin is a cryptocurrency designed to maintain a fixed value, almost always pegged to $1 USD. Unlike Bitcoin or Ethereum, which can swing 10% in a single day, stablecoins exist to be boring. They serve as the settlement layer between volatile crypto assets and the traditional financial system.
Traders use stablecoins to park profits without converting back to fiat currency. DeFi protocols use them as the base asset for lending, borrowing, and liquidity pools. Remittance senders use them to move dollars across borders in minutes instead of days. By early 2026, the combined market cap of all stablecoins sat at approximately $235 billion, with Tether (USDT) and USD Coin (USDC) controlling more than 80% of the market between them.
The critical question is not whether stablecoins are useful. That debate ended years ago. The question is what actually backs them and what happens when the backing fails. Three distinct mechanical models have emerged, each with different trade-offs between decentralization, capital efficiency, and risk.
| Feature | Fiat-Backed | Crypto-Collateralized | Algorithmic |
|---|---|---|---|
| Examples | USDT, USDC, BUSD, PYUSD | DAI, LUSD, sUSD | UST (collapsed), FRAX, AMPL |
| Reserve Type | Cash, T-bills, money market funds | ETH, BTC, or other crypto locked in smart contracts | No reserves; relies on mint/burn algorithms |
| Collateral Ratio | 1:1 (each token backed by $1 in reserves) | 150%+ over-collateralized | 0% to partial (undercollateralized by design) |
| Peg Mechanism | Direct redemption for $1 from issuer | Arbitrage + liquidation of undercollateralized vaults | Direct redemption for $1 from the issuer |
| Centralization | High (single issuer controls reserves) | Low to moderate (governed by DAO) | Low (code-driven) |
| Key Risk | Issuer insolvency, reserve composition opacity | Crypto crash cascading into mass liquidations | Death spiral when confidence breaks |
| Regulatory Status (2026) | Licensed under MiCA (EU); GENIUS Act pending (US) | Unclear regulatory classification in most jurisdictions | Effectively banned or restricted post-Terra |
Sources: CoinGecko, DefiLlama, European Securities and Markets Authority
How Fiat-Backed Stablecoins Work
Fiat-backed stablecoins operate on the simplest model: for every token in circulation, the issuer holds an equivalent amount of real-world assets in reserve. When you hold 1 USDC, Circle claims to hold $1 in cash or short-term US Treasury bills on your behalf. When you hold 1 USDT, Tether makes the same claim.
The peg holds because of a direct redemption mechanism. Authorized participants (typically institutional users and exchanges) can send stablecoins back to the issuer and receive dollars in return. If USDC trades at $0.99 on an exchange, an arbitrageur buys it at a discount, redeems it with Circle for $1.00, and pockets the difference. This buying pressure pushes the price back to $1. The reverse applies when the token trades above $1: participants deposit dollars, mint new tokens, and sell them at a premium.
What Sits in the Reserves
Not all fiat-backed stablecoins hold the same assets. Circle publishes monthly attestation reports showing USDC reserves are held primarily in short-dated US Treasury bills and cash deposits at regulated banks. Tether has historically been less transparent, though its quarterly attestation reports show a shift toward US Treasuries since 2023. By Q4 2025, Tether reported holding over $113 billion in US Treasury bills, representing more than 75% of its total reserves.
The composition of reserves matters because it determines how quickly an issuer can actually honor redemptions. Cash and short-term Treasuries can be liquidated in hours. Corporate bonds, secured loans, or other less liquid assets take longer, and their value can fluctuate. This distinction became painfully relevant when USDC briefly fell to $0.87 in March 2023 after Circle disclosed that $3.3 billion of its reserves were trapped at the collapsing Silicon Valley Bank.
How a USDC Redemption Works
The redemption process is the engine that keeps fiat-backed stablecoins pegged. Here is how a standard USDC redemption flows from start to finish.
| Step | Action | Who Acts | Time Frame |
|---|---|---|---|
| 1 | Authorized participant submits USDC tokens to Circle via the Circle Mint platform | Institutional redeemer | Minutes |
| 2 | Circle verifies the redemption request and KYC/AML compliance | Circle compliance team | Minutes to hours |
| 3 | Circle burns the submitted USDC tokens, permanently removing them from circulation | Circle smart contract | Seconds (on-chain) |
| 4 | Circle instructs its banking partner to wire the equivalent USD to the redeemer | Circle treasury operations | Same business day |
| 5 | Redeemer receives USD in their bank account; total USDC supply decreases by the redeemed amount | Banking system | 1 to 2 business days |
Source: Circle USDC documentation
This process works smoothly under normal conditions. The risk emerges during periods of mass redemption, when the issuer must liquidate reserves quickly enough to meet demand. Circle processed over $8 billion in net redemptions during the SVB crisis week in March 2023, stress-testing its reserve liquidity in real time.
How Crypto-Collateralized Stablecoins Work
Crypto-collateralized stablecoins take a fundamentally different approach. Instead of trusting a company to hold dollars in a bank, users lock cryptocurrency into smart contracts and mint stablecoins against that collateral. The most established example is DAI, created by MakerDAO (now rebranded as Sky) on Ethereum.
The core problem this model solves is trust. No single company controls DAI’s reserves. The collateral sits in transparent, auditable smart contracts on the Ethereum blockchain. Anyone can verify the total collateral backing DAI at any moment. The trade-off is capital inefficiency: you must lock up significantly more value than you receive.
MakerDAO Vaults and Over-Collateralization
To mint DAI, a user opens a Vault (formerly called a Collateralized Debt Position, or CDP) by depositing cryptocurrency, typically ETH or WBTC. The system requires a minimum collateral ratio of 150% for most asset types. This means depositing $150 worth of ETH to mint 100 DAI (worth $100).
The over-collateralization creates a safety buffer. If the price of ETH drops, the collateral ratio falls. If it reaches the liquidation threshold (typically 150% for ETH-backed Vaults), the system automatically auctions off the collateral to repay the DAI debt. This liquidation mechanism is what keeps DAI solvent even during sharp market downturns.
Consider a practical example. A user deposits $3,000 worth of ETH and mints 1,000 DAI. Their collateral ratio is 300%. ETH then drops 60% in value, reducing the collateral to $1,200. The ratio falls to 120%, below the 150% threshold. The Maker Protocol automatically liquidates enough collateral to bring the Vault back to health or close it entirely. The user keeps their 1,000 DAI, but loses a portion of their ETH collateral plus a 13% liquidation penalty.
How DAI Maintains Its Peg
DAI’s peg mechanism relies on two forces: arbitrage and the Dai Savings Rate (DSR). When DAI trades above $1, users are incentivized to open new Vaults, mint DAI, and sell it at a premium. This increases supply and pushes the price down. When DAI trades below $1, holders can buy it cheaply and use it to repay Vault debt at face value, effectively getting a discount on their loan repayment. This reduces supply and pushes the price up.
MakerDAO governance can also adjust the Stability Fee (the interest rate on Vault borrowing) and the DSR (the yield paid to DAI holders who deposit into the savings contract) to influence supply and demand. Raising the Stability Fee makes minting DAI more expensive, reducing supply. Raising the DSR makes holding DAI more attractive, increasing demand.
How Algorithmic Stablecoins Work (and Why They Fail)
Algorithmic stablecoins attempted to solve the biggest criticism of both previous models. Fiat-backed stablecoins require trusting a centralized issuer. Crypto-collateralized stablecoins lock up capital inefficiently. Algorithmic designs promised a stablecoin backed by nothing but code, maintaining its peg through automatic supply adjustments.
The theory works like this: when the token trades above $1, the algorithm mints new tokens to increase supply and push the price down. When it trades below $1, the algorithm removes tokens from circulation (through burning or bond mechanisms) to decrease supply and push the price up. No reserves required. No collateral locked. Pure monetary policy executed by smart contracts.
The Terra Collapse: A Case Study in Algorithmic Failure
TerraUSD (UST) was the largest algorithmic stablecoin, reaching a peak market cap of approximately $18.7 billion in early May 2022. It maintained its peg through a mint-burn relationship with its sister token LUNA. Users could always swap 1 UST for $1 worth of LUNA, and vice versa. If UST dropped to $0.98, arbitrageurs would buy it and swap for $1 worth of LUNA, pocketing the $0.02 difference while reducing UST supply.
The system’s fatal dependency was demand. Anchor Protocol generated that demand by offering approximately 20% APY on UST deposits, a yield subsidized by Terra’s reserve fund rather than organic economic activity. When large holders began withdrawing from Anchor in early May 2022, the reflexive mechanism reversed: UST selling created LUNA minting, LUNA selling crashed LUNA’s price, and the declining LUNA price meant each UST redemption minted even more LUNA.
The death spiral was completed in five days. UST fell from $1.00 to $0.01. LUNA fell from $64 to fractions of a penny. Approximately $45 billion in combined value was destroyed. Do Kwon, Terra’s co-founder, was arrested in Montenegro in March 2023 and faced extradition proceedings. The complete timeline of this collapse is covered in our history of stablecoins.
The fundamental flaw was circular: UST’s value depended on LUNA’s value, and LUNA’s value depended on UST’s adoption. When confidence broke, both assets entered a reflexive downward spiral with no external collateral to absorb the losses. Every algorithmic stablecoin that relied on a similar dual-token model, including NuBits years earlier, has faced the same structural vulnerability.
Peg Mechanisms: How Stablecoins Maintain $1
Every stablecoin depends on arbitrage to hold its peg. The specific mechanisms differ, but the underlying principle is the same: when the price deviates from $1, someone must be financially incentivized to push it back. If those incentives break down, the peg breaks.
| Scenario | Fiat-Backed Response | Crypto-Collateralized Response | Algorithmic Response |
|---|---|---|---|
| Token trades at $0.98 | Arbitrageur buys at $0.98, redeems with issuer for $1.00, profits $0.02 | Holder buys at $0.98, repays $1.00 of Vault debt, saves $0.02 per token | Algorithm burns tokens to reduce supply; arbitrageur swaps for $1 of paired token |
| Token trades at $1.02 | Arbitrageur mints new tokens for $1.00, sells at $1.02, profits $0.02 | User opens Vault, mints at face value, sells at $1.02 premium | Algorithm mints new tokens to increase supply |
| Mass sell-off event | Issuer liquidates reserves to honor redemptions; peg holds if reserves are liquid | Liquidation cascade sells collateral; peg recovers if system is over-collateralized | Spiral risk: selling pressure mints more paired tokens, crashing both |
| Confidence crisis | Liquidation cascade sells collateral; peg recovers if the system is over-collateralized | Peg depends on smart contract solvency (verifiable on-chain) | Peg collapses because the model has no backstop beyond market confidence |
Sources: Federal Reserve Board, Bank for International Settlements
The speed of arbitrage matters as much as the mechanism itself. USDT and USDC arbitrage opportunities close in seconds on major exchanges because of high liquidity and tight spreads. DAI corrections take longer because they require on-chain transactions with gas fees. Algorithmic peg corrections are slowest because they depend on market participants trusting that the mechanism will work, a trust that evaporates precisely when it is needed most.
One pattern stands out across all three models: stablecoins never break their peg upward in a sustained way. The $1 ceiling holds because minting new tokens is straightforward. Every peg failure in stablecoin history has been a downward break, where redemption demand exceeded the system’s ability to absorb it. This asymmetry is the defining risk of the entire asset class.
Regulation and Reserve Audits
For most of stablecoin history, issuers operated with minimal oversight. Tether famously avoided a full audit for years, relying instead on periodic “attestation reports” from accounting firms. These reports confirmed what assets Tether held on a specific date, but they did not verify that those reserves existed continuously or that they could be liquidated quickly enough to meet redemptions during a crisis.
That era is ending. Two regulatory frameworks are now reshaping how stablecoins must operate.
MiCA (Markets in Crypto-Assets Regulation)
The EU’s MiCA regulation took full effect in December 2024, making the European Union the first major jurisdiction to create a formal stablecoin licensing framework. Under MiCA, any stablecoin issuer operating in the EU must maintain 100% reserve backing at all times, with reserves held in custody at regulated credit institutions. Issuers must obtain authorization as an Electronic Money Institution (EMI) or credit institution.
MiCA also imposes daily transaction volume limits on stablecoins not denominated in euros. If a non-euro stablecoin exceeds 1 million transactions or 200 million euros in daily volume within the EU, the issuer must take steps to reduce usage. This provision was explicitly designed to limit the dominance of US dollar stablecoins within the European financial system.
The GENIUS Act (United States)
In the United States, the Guiding and Establishing National Innovation for US Stablecoins (GENIUS) Act was introduced in early 2025 with bipartisan support. The bill proposes a federal licensing framework requiring stablecoin issuers to maintain 1:1 reserves in cash, short-term US Treasuries, or central bank deposits. It would mandate monthly public reserve disclosures and annual audits by registered public accounting firms.
The GENIUS Act also creates a two-tier system: issuers with more than $10 billion in outstanding stablecoins would be regulated federally, while smaller issuers could opt for state-level regulation. As of early 2026, the bill has passed committee review but awaits a full Senate vote.
Attestation vs. Audit: The Difference That Matters
The distinction between an attestation and a full audit is critical for evaluating stablecoin reserve claims. An attestation is a point-in-time snapshot: an accounting firm confirms what assets the issuer held on a specific date. A full audit examines records over an entire period, tests internal controls, and provides reasonable assurance that the financial statements are accurate.
| Feature | Attestation Report | Full Financial Audit |
|---|---|---|
| Scope | Single point in time (e.g., June 30, 2025) | Entire reporting period (e.g., full year 2025) |
| What It Verifies | Assets held on that specific date | Financial position, internal controls, and transactions over the period |
| Standard Used | AICPA AT-C 205 (examination) | PCAOB or AICPA auditing standards |
| Assurance Level | Limited (confirms a snapshot, not ongoing solvency) | Reasonable (highest level of assurance) |
| Who Uses It | Circle (monthly), Tether (quarterly), Paxos | The issuer could theoretically move assets the day after attestation |
| Limitation | Issuer could theoretically move assets the day after attestation | Tests for this exact risk through continuous monitoring and sampling |
Sources: AICPA, European Banking Authority
In March 2026, Tether announced it had engaged KPMG for a full reserve audit, a significant shift after years of criticism. Circle already publishes monthly attestation reports from Deloitte and has signaled it would comply with full audit requirements under the GENIUS Act. The regulatory direction is clear: the era of self-reported reserve claims is ending, and stablecoin issuers will face the same scrutiny as traditional financial institutions.
Frequently Asked Questions (FAQs)
Fiat-backed stablecoins like USDT and USDC are backed by reserves including US dollars, Treasury bills, and money market funds held by the issuing company. Crypto-collateralized stablecoins like DAI are backed by cryptocurrency locked in smart contracts at a ratio of 150% or higher. Algorithmic stablecoins have no reserves and rely on code to adjust supply.
Yes. Stablecoins can and do lose their peg. TerraUSD collapsed from $1.00 to $0.01 in May 2022. USDC fell to $0.87 during the Silicon Valley Bank crisis in March 2023 before recovering. Every stablecoin’s peg depends on the strength of its reserves or collateral and on market participants’ willingness to arbitrage price deviations.
Both are fiat-backed stablecoins pegged to $1, but they differ in transparency and regulation. USDC is issued by Circle, publishes monthly attestation reports from Deloitte, and holds reserves primarily in US Treasuries and cash. USDT is issued by Tether, publishes quarterly attestation reports, and has historically faced criticism for limited reserve transparency, though it announced a full KPMG audit in 2026.
Fiat-backed stablecoins from licensed issuers carry lower risk than other types, but they are not risk-free. Risks include issuer insolvency, reserve liquidity problems, regulatory action, and smart contract vulnerabilities. No stablecoin carries deposit insurance like a bank account. The safest approach is to understand exactly what backs the stablecoin you hold and whether the issuer is regulated.
Algorithmic stablecoins fail because their peg depends entirely on market confidence, with no external collateral as a backstop. When selling pressure exceeds the algorithm’s ability to contract supply, a death spiral begins: falling prices trigger more selling, which triggers more token minting, which crashes the paired token’s value. The TerraUST collapse in May 2022 is the most prominent example of this failure mode.
Conclusion
The three stablecoin models represent three different answers to the same question: how do you create a digital dollar that holds its value? Fiat-backed tokens chose simplicity and trust in a central issuer. Crypto-collateralized tokens chose transparency and decentralization at the cost of capital efficiency. Algorithmic tokens chose elegance and zero collateral, then discovered that monetary policy without a backstop collapses under stress.
The market has delivered its verdict. Fiat-backed stablecoins control over 90% of the total stablecoin market capitalization. Crypto-collateralized designs like DAI serve a meaningful niche in DeFi but have not scaled to rival USDT or USDC. No algorithmic stablecoin has recovered credibility since Terra. Regulation is now formalizing what the market already decided: if you issue a token that promises to be worth $1, you need to prove you can honor that promise, not with code alone, but with real assets and audited books.
The next chapter will be defined by how issuers adapt to MiCA in Europe and whatever framework emerges from the GENIUS Act in the United States. Stablecoins that meet these standards will become regulated financial instruments indistinguishable in function from bank deposits. Those who do not will be pushed to the margins. For anyone holding, trading, or building on stablecoins, understanding the mechanics behind the peg is no longer optional knowledge.
