What Frax was built to do
FRAX launched in 2020 as the first widely adopted "fractional-algorithmic" stablecoin: a portion of every FRAX in circulation was backed by collateral, typically USDC, while the remainder was stabilised algorithmically through the protocol's FXS token, which absorbed volatility by expanding or contracting supply in response to demand. The collateral ratio adjusted dynamically based on market conditions, in theory letting Frax Finance use capital more efficiently than fully-collateralised stablecoins like USDC while still holding its dollar peg.
Why it's now "legacy"
Frax Finance moved decisively away from that hybrid model over time, pushing FRAX toward full collateralisation and eventually launching frxUSD as its new flagship stablecoin, built for cleaner integration with real-world asset yield and institutional collateral standards under the protocol's Frax v3 architecture. FRAX itself has been relabelled "legacy" as the protocol steers liquidity, incentives and development focus toward frxUSD, alongside Fraxtal, Frax's own Ethereum layer 2. Holding legacy FRAX today means holding a stablecoin the issuing protocol itself is actively de-emphasising in favour of its successor.
Risks worth knowing
FRAX's algorithmic-era design carried real peg risk, most visibly in March 2023 when USDC itself briefly depegged during the Silicon Valley Bank collapse — since FRAX's collateral was heavily USDC-based, FRAX wobbled in sympathy, a reminder that fractional-algorithmic stability is only as strong as its weakest collateral link. That specific mechanism has since been phased down, but legacy FRAX now carries a different risk: shrinking liquidity, reduced protocol support, and declining relevance as users and integrations migrate to frxUSD. Anyone holding or using FRAX should treat it as a wind-down asset rather than Frax Finance's active flagship product, and check current collateralisation and redemption terms directly rather than assuming the original fractional-algorithmic model still applies.