- Frax Finance Internals

How Frax works in 90 seconds

Frax was the first fractional-algorithmic stablecoin - it launched with a 100% collateral ratio and has been gradually reducing that ratio as FRAX adoption grows and the market demonstrates confidence. The system has three core tokens: FRAX (the stablecoin), FXS (the governance token), and frxETH (an ETH-pegged staking derivative that lets Frax offer ETH-native financial products). Every FRAX in circulation is backed by a combination of collateral (USDC, ETH, etc.) and an algorithmic expectation backed by the Frax AMO controller.

The AMO is the heart of the system. It runs a PID control loop that reads FRAX's 24-hour TWAP on Curve. When the TWAP exceeds $1.002, the AMO expands: it mints new FRAX from idle collateral sitting in the CurveFRAX pool, sells that FRAX for the collateral asset, and either deposits the proceeds into the Surplus Buffer (which funds FXS buybacks) or deploys them into Aave/Compound to earn yield. When the TWAP falls below $0.998, the AMO contracts: it buys FRAX on the open market using the Surplus Buffer and burns it, raising the collateral ratio. The net effect is a self-balancing peg maintenance engine that generates revenue for FXS holders.

FXS is purely a governance and value-accrual token. There is no staking yield on FXS - its value comes from the protocol using the Surplus Buffer to buy FXS on the open market and burn it. veFXS is earned by time-locking FXS for up to four years; veFXS holders vote on biweekly gauge weights that decide how Frax Credit Asset (FCA) protocol emissions are distributed across pools, including Fraxswap, bridged Curve pools, and lending markets. Protocols and traders bribe veFXS holders through the same marketplaces used for veCRV, creating an analogous liquidity-rental economy. Frax's all-chain strategy puts FRAX as native infrastructure on Fraxtal and Mode (its own L2s) and bridges it across ten-plus chains via LayerZero and Wormhole, competing to be the universal settlement stablecoin.

Key concepts

Fractional-algorithmic design

Frax sits between fully collateralized stablecoins (USDC, DAI) and purely algorithmic ones (Ampleforth, Empty Set Dollar). Every FRAX has a collateral ratio: e.g. at 82% CR, 82 of every FRAX is backed by real collateral (USDC, wETH) and 18 is backed by the algorithmic expectation that FRAX will trade at $1. As adoption grows and the AMO generates surplus, the CR is incrementally lowered - the protocol "learns" to trust itself over time.

AMO controller

The Algorithmic Market Operations controller is an autonomous contract that monitors FRAX's TWAP price on Curve and decides whether to expand or contract the FRAX supply. Expansion means minting FRAX against idle collateral and selling it on Curve into the Surplus Buffer; contraction means buying FRAX back and burning it. The AMO is essentially the monetary policy committee - a piece of code that adjusts the money supply without human interference. Governance can pause or override it at any time.

Collateral ratio (CR)

The percentage of every FRAX that is backed by real collateral. At 100% CR, 1 FRAX = $1 of collateral locked. At 80% CR, 1 FRAX = $0.80 of collateral + $0.20 of algorithmic backing. The CR is set by an on-chain PID controller reading the FRAX TWAP; governance has set a floor of 80% on mainnet. The CR is visible in real time on Frax's dashboard and is the primary signal for how much market confidence the system has earned.

CurveFRAX pool

The Curve FRAX/USDC (or FRAX3CRV) StableSwap pool is the primary venue where FRAX discovers its peg. Because Curve's StableSwap invariant has near-zero slippage for pegged assets, large FRAX mints and burns execute close to $1. The pool also accumulates trading fees, which are split between LPs and the Frax Surplus Buffer via the AMO's autocompounding mechanism.

veFXS and gauge weights

FXS can be time-locked for up to four years in exchange for veFXS, which grants voting rights over FCA (Frax Credit Asset) emissions. Every two weeks, veFXS holders vote on gauge weights that distribute new FCA tokens to approved pools - Fraxswap pairs, bridged Curve pools, Fraxlend markets, and others. Protocols and traders post bribes (in FXS, USDC, or other tokens) to veFXS holders to redirect FCA emissions toward pools that benefit them, mirroring the Curve Wars bribe economy.

Fraxswap and Fraxlend

Fraxswap is Frax's custom AMM, forked from Solidly/Velodrome, that uses an asymmetric bonding curve designed specifically for FRAX pair pools. It offers lower fees than Curve for FRAX-native pairs and integrates directly with veFXS gauges. Fraxlend is a permissionless lending market where users can deposit collateral and borrow FRAX or other assets against it, with interest rates set by an algorithmic curve tied to utilization. Both products are core to the Frax ecosystem flywheel.

Fraxtal and Mode (L2)

Fraxtal and Mode are Frax's own L2 rollups, built on the OP Stack. Unlike most L2s that use ETH as gas, Fraxtal and Mode use FRAX as the gas currency - making FRAX a productive asset from day one on those chains rather than a neutral settlement token. Frax also uses its L2 position to deploy the full Frax Finance stack (FRAX, frxETH, Fraxswap, Fraxlend) as native primitives, creating a self-reinforcing DeFi ecosystem where FRAX is simultaneously the stablecoin, the gas token, and the collateral asset.

Why Frax matters

Frax introduced the idea that a stablecoin's collateral ratio could be a market-signal-driven variable rather than a fixed governance parameter. That insight - that a protocol could progressively "decentralize" its monetary policy by demonstrating peg stability - inspired a generation of fractional stablecoin designs and created an autonomous yield engine (the AMO) that funds FXS buybacks without diluting existing holders. The all-chain expansion strategy, culminating in Fraxtal and Mode where FRAX is the gas token, represents the most ambitious attempt in DeFi to make a stablecoin the fundamental settlement layer of an entire blockchain ecosystem.

As of 2026 Frax manages around $1.8B in TVL, with FRAX circulating across ten chains, frxETH staking derivatives competing with Lido, and Fraxlend providing permissionless credit markets. The veFXS bribe economy rivals veCRV's in sophistication, and Frax's integration with Convex means that a large portion of Curve's stablecoin LP infrastructure is indirectly Frax-controlled. Understanding Frax is essential for anyone building or analyzing the stablecoin ecosystem - it is the only protocol that treats its own governance token as the residual claimant to a fully self-managing monetary system.

Frequently asked questions

What makes Frax the first fractional-algorithmic stablecoin?

Frax was designed from the start to scale down its collateral ratio as adoption grows, starting at 100% collateral and moving toward an algorithmic backbone. Where a purely algorithmic stablecoin like Ampleforth has no collateral backstop, Frax always retains a collateral ratio - the fractional part - which shrinks over time as market confidence in FRAX grows. This makes it the first protocol to bridge the full spectrum from fully collateralized to fully algorithmic.

How does the AMO controller actually work?

The AMO (Algorithmic Market Operations) controller is the core revenue engine. It monitors FRAX's market price relative to $1. If FRAX > $1, it expands supply by minting new FRAX from idle collateral, selling it on Curve, and depositing proceeds into the Surplus Buffer. If FRAX < $1, it contracts: buying FRAX on the open market (using the buffer or borrowing) and burning it, which raises the collateral ratio. The AMO can also deploy idle collateral into lending markets (Aave, Compound) to earn yield while staying redeemable.

What determines the Collateral Ratio, and who controls it?

The CR is set by an on-chain PID controller that reads FRAX's 24-hour TWAP price and adjusts the ratio in steps. When the TWAP is above $1.002, the controller incrementally lowers the CR (making FRAX more algorithmic), and when the TWAP falls below $0.998, it raises the CR. Governance can override the controller or set CR floors/ceilings directly. As of 2026, the CR floor is 80% on mainnet, meaning at least 80 cents of every FRAX is always backed by real collateral.

How does veFXS differ from veCRV in its economic design?

veFXS is earned by staking FXS and scales linearly with lock time up to four years. The key difference is that Frax uses a gauge system borrowed from Solidly/Velodrome: veFXS holders vote biweekly on how to split FCA (Frax Credit Asset) emissions across approved gauge pools. Those gauges can include Fraxswap pools, external Curve pools bridged via Ankr or Across, and lending markets. Bribes flow from protocols wanting to redirect FCA emissions, creating a live rental market for FRAX ecosystem liquidity similar to the CRV bribe economy.

What is the Fraxferral referral system?

Fraxferral is an on-chain referral program that rewards users who bring new capital into Frax's products. When a referred user deposits into Fraxswap, Fraxlend, or the Fraxsolid pools, the referrer earns a cut of the trading fees or interest earned - typically 5-10% of the referee's activity for 30 days. This created a large viral flywheel that drove adoption of FRAX across Curve, Convex, and Yearn vault users.

How does Frax maintain its peg compared to DAI or USDC?

Unlike USDC (fiat-backed, custodial) or DAI (overcollateralized, governance-managed), FRAX maintains its peg through a combination of arbitrage and the AMO. When FRAX trades above $1, anyone can deposit $1 worth of collateral and mint 1 FRAX to sell at a profit - this is direct arbitrage that expands supply. When FRAX trades below $1, anyone may purchase FRAX and redeem it for $1 worth of collateral at the current CR. The AMO front-runs these arb opportunities to keep the peg within a tight band, and the Surplus Buffer absorbs losses before the CR must be raised.

What is Frax's strategy for becoming an all-chain stablecoin?

Frax launched on Ethereum, then bridged to Arbitrum, Optimism, Base, Polygon, Avalanche, BNB Chain, Fantom, Gnosis, and its own Fraxtal L2 - in each case deploying the Frax Finance stack (FRAX, frxETH, Fraxswap, Fraxlend) as native infrastructure. Fraxtal and Mode are EVM-compatible L2s where FRAX is the primary gas token, meaning DeFi activity on those chains inherently circulates FRAX. Frax also bridges its stablecoin infrastructure to partner chains via LayerZero and Wormhole, competing to be the universal stablecoin settlement layer.

Related reading

• Curve Finance - the StableSwap AMM powering FRAX's primary peg discovery venue and the source of the veCRV bribe economy Frax participates in.
• MakerDAO / Sky - compare Frax's fractional-algorithmic AMO to Maker's stability fee / DSR / PSM monetary policy toolkit.
• Stablecoin peg mechanisms - see where Frax's AMO-driven peg defense slots in next to DAI's PSM, USDC's fiat reserve model, and Ethena's delta-hedged USDe.
• veFXS mechanics - deep dive into FXS locking, gauge voting, FCA emissions, and the bribe marketplace that funds Frax's liquidity wars.
• Fraxtal & Mode - how Frax built L2 chains where FRAX is the native gas token and the full DeFi stack deploys on day one.