What is Algorithmic Stablecoin?
How it works
Algorithmic stablecoins maintain their peg through supply adjustments encoded in smart contracts. When the market price rises above the target (e.g., $1), the protocol mints new tokens and distributes them to users, increasing supply and pushing the price back down. Conversely, when the price falls below the peg, the protocol reduces supply by buying back and burning tokens, or by offering incentives for users to lock or destroy their tokens. This mechanism relies on arbitrageurs who profit from price discrepancies, helping to stabilize the system.
A common design involves a two-token system: a stablecoin and a volatile 'share' or 'bond' token. For example, in the Terra ecosystem, UST was the stablecoin and LUNA was the volatile token. When UST demand rose, LUNA was burned to mint UST, reducing LUNA supply and increasing its value. When UST demand fell, UST was burned to mint LUNA, absorbing excess supply. This creates a reflexive relationship where the volatile token absorbs price shocks. However, such systems are vulnerable to death spirals if confidence collapses, as seen in Terra's 2022 crash.
Other implementations use rebase mechanisms, where the total supply of the stablecoin adjusts automatically across all holders' wallets. For instance, Ampleforth (AMPL) targets a 2019 USD peg by expanding or contracting supply daily based on price. If AMPL trades above $1, wallets see their balances increase proportionally; if below, balances decrease. This direct supply adjustment aims to align purchasing power without requiring collateral, but it introduces volatility in wallet balances and can be disorienting for users.
Why it matters
Algorithmic stablecoins represent a purely decentralized approach to stable value, free from reliance on centralized reserves or overcollateralization. They could enable censorship-resistant stable assets for global payments and DeFi. However, their history of catastrophic failures, like TerraUSD's collapse, highlights critical risks of reflexive design and the need for robust mechanisms. Understanding them is vital for assessing the future of decentralized money and the trade-offs between autonomy and stability.
Real-world examples
TerraUSD (UST) was the most prominent algorithmic stablecoin, pegged to $1 via LUNA's mint-and-burn mechanism until its 2022 collapse. Ampleforth (AMPL) uses a daily rebase to target a 2019 USD peg. Frax Finance initially launched as a fractional-algorithmic stablecoin (FRAX) before transitioning to fully collateralized. Basis Cash was an early seigniorage-style project that failed to maintain its peg.
FAQ
How do algorithmic stablecoins differ from collateralized stablecoins?
Collateralized stablecoins like USDC are backed by fiat or crypto reserves held in custody, while algorithmic stablecoins use smart contract rules to adjust supply and maintain their peg without direct collateral backing.
What caused the TerraUSD crash?
TerraUSD (UST) lost its peg in May 2022 due to a bank run triggered by large withdrawals from its Anchor Protocol, leading to a death spiral where LUNA hyperinflated and UST collapsed to near zero.
Are algorithmic stablecoins still used today?
Yes, projects like Ampleforth (AMPL) and Frax (FRAX) continue to operate, though many have moved toward hybrid models with partial collateralization to improve resilience.
Related terms
Go deeper
Browse the complete crypto glossary to explore related terms and concepts.
Browse Glossary