Balancer V2 (balancer-v2)

In a Sauce program, swap with @sauce/router’s function for the venue (uniswapV2, uniswapV3, uniswapV4, curve, balancerV2, …; Slipstream, PancakeSwap V3 and Algebra pools through uniswapV3), with a minimum output and, where the pool takes one, a price limit (the @sauce/router reference; several pools under one limit, the distributed swap).

​

What it offers

• swap: Execute a single swap through the Vault specifying pool ID and assets
• addLiquidity: Join a pool by depositing tokens via the Vault
• removeLiquidity: Exit a pool by withdrawing tokens via the Vault

​

Notes

• Single Vault contract holds ALL pool liquidity (same address 0xBA12... on every chain)
• Pools are identified by bytes32 poolId, NOT by contract address
• The Vault model means tokens only need to be approved to ONE contract for all Balancer pools
• Weighted pools: custom token weights (e.g., 80/20 ETH/USDC); Stable pools: pegged assets; Linear pools: wrapping yield-bearing tokens
• batchSwap is gas-efficient for multi-hop trades since tokens only move between Vault internal accounts
• Flash loans from Balancer Vault are zero-fee when the swap route stays within Balancer pools
• Internal balances: users can keep tokens in the Vault to save gas on repeated trades
• userData encoding varies by pool type - check Balancer docs for the specific pool’s join/exit types
• Use Balancer for multi-token pools (3+ tokens), weighted index exposure, or flash loans
• From a Pot program, @sauce/router swaps through the Vault directly: balancerV2(vault, tokenIn, tokenOut, amountIn, poolId, minOut, recipient) approves the Vault for exactly amountIn and calls swap (GIVEN_IN, internal balances off) with minOut as its limit, returning the amount out; the allowance ends at zero. tryBalancerV2 catches a failed swap, resets the approval and returns 0. The balancerV2Swap action is the same call

​

Its names in a program

function main() {
  // Ethereum's vault, `0xBA12222222228d8Ba445958a75a0704d566BF2C8`.
  require(BalancerV2.Vault != 0);
}

​

Deployments

​

ABI

​

BalancerV2VaultABI

• swap((bytes32 poolId, uint8 kind, address assetIn, address assetOut, uint256 amount, bytes userData) singleSwap, (address sender, bool fromInternalBalance, address recipient, bool toInternalBalance) funds, uint256 limit, uint256 deadline) payable returns (uint256 amountCalculated)
• batchSwap(uint8 kind, (bytes32 poolId, uint256 assetInIndex, uint256 assetOutIndex, uint256 amount, bytes userData)[] swaps, address[] assets, (address sender, bool fromInternalBalance, address recipient, bool toInternalBalance) funds, int256[] limits, uint256 deadline) payable returns (int256[] assetDeltas)
• joinPool(bytes32 poolId, address sender, address recipient, (address[] assets, uint256[] maxAmountsIn, bytes userData, bool fromInternalBalance) request) payable
• exitPool(bytes32 poolId, address sender, address recipient, (address[] assets, uint256[] minAmountsOut, bytes userData, bool toInternalBalance) request)
• flashLoan(address recipient, address[] tokens, uint256[] amounts, bytes userData)
• getPoolTokens(bytes32 poolId) view returns (address[] tokens, uint256[] balances, uint256 lastChangeBlock)

​

Next steps

• Protocols: the other protocols, by what they do.
• Protocols and tokens: calling a contract by its namespace, or through its ABI.
• Glossary: the words these pages use, in plain terms.