Router API
The Router can be used to interact with Balancer onchain via state changing operations or used to query operations in an off-chain context.
State-changing functions
The router's state-changing functions are used for interacting with Balancer onchain. They provide simple interfaces for the most common user actions performed against the Balancer Vault.
Pool initialization
initialize
function initialize(
address pool,
IERC20[] memory tokens,
uint256[] memory exactAmountsIn,
uint256 minBptAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256 bptAmountOut);
This function initializes a liquidity pool. It adds the initial liquidity to the pool and mints the initial pool tokens.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokens | IERC20[] | Array of token contracts to be added to the pool |
| exactAmountsIn | uint256[] | Exact amounts of tokens to be added, sorted in token registration order |
| minBptAmountOut | uint256 | Minimum amount of pool tokens to be received |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding initial liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountOut | uint256 | Actual amount of pool tokens minted in exchange for initial liquidity |
Add liquidity
addLiquidityProportional
function addLiquidityProportional(
address pool,
uint256[] memory maxAmountsIn,
uint256 exactBptAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256[] memory amountsIn);
Adds with proportional token amounts to a pool, receiving an exact amount of pool tokens.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxAmountsIn | uint256[] | Maximum amounts of tokens to be added, sorted in token registration order |
| exactBptAmountOut | uint256 | Exact amount of pool tokens to be received |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsIn | uint256[] | Actual amounts of tokens added, sorted in token registration order |
addLiquidityUnbalanced
function addLiquidityUnbalanced(
address pool,
uint256[] memory exactAmountsIn,
uint256 minBptAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256 bptAmountOut);
Adds with arbitrary token amounts in to a pool.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactAmountsIn | uint256[] | Exact amounts of tokens to be added, sorted in token registration order |
| minBptAmountOut | uint256 | Minimum amount of pool tokens to be received |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountOut | uint256 | Actual amount of pool tokens received |
addLiquiditySingleTokenExactOut
function addLiquiditySingleTokenExactOut(
address pool,
IERC20 tokenIn,
uint256 maxAmountIn,
uint256 exactBptAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256 amountIn);
Adds with a single token to a pool, receiving an exact amount of pool tokens.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token used to add liquidity |
| maxAmountIn | uint256 | Maximum amount of tokens to be added |
| exactBptAmountOut | uint256 | Exact amount of pool tokens to be received |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| amountIn | uint256 | Actual amount of tokens added |
donate
function donate(
address pool,
uint256[] memory amountsIn,
bool wethIsEth,
bytes memory userData
) external payable;
Adds liquidity to a pool by donating the amounts in (no BPT out). To support donation, the pool config enableDonation flag must be set to true. This liquidity type is disabled by default, and is only useful in certain limited use cases (e.g., pools with exit fees). Pools that support donation have special security considerations. In particular, their rates are trivially manipulable, so they cannot be nested inside other pools. Use with care!
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| amountsIn | uint256[] | Amounts of tokens to be donated, sorted in token registration order |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding liquidity |
addLiquidityCustom
function addLiquidityCustom(
address pool,
uint256[] memory maxAmountsIn,
uint256 minBptAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256[] memory amountsIn, uint256 bptAmountOut, bytes memory returnData);
Adds liquidity to a pool with a custom request.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxAmountsIn | uint256[] | Maximum amounts of tokens to be added, sorted in token registration order |
| minBptAmountOut | uint256 | Minimum amount of pool tokens to be received |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH; otherwise the Vault will pull WETH tokens |
| userData | bytes | Additional (optional) data required for adding liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsIn | uint256[] | Actual amounts of tokens added, sorted in token registration order |
| bptAmountOut | uint256 | Actual amount of pool tokens received |
| returnData | bytes | Arbitrary (optional) data with encoded response from the pool |
Remove liquidity
removeLiquidityProportional
function removeLiquidityProportional(
address pool,
uint256 exactBptAmountIn,
uint256[] memory minAmountsOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256[] memory amountsOut);
Removes liquidity with proportional token amounts from a pool, burning an exact pool token amount.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | Exact amount of pool tokens provided |
| minAmountsOut | uint256[] | Minimum amounts of tokens to be received, sorted in token registration order |
| wethIsEth | bool | If true, outgoing WETH will be unwrapped to ETH; otherwise the Vault will send WETH tokens |
| userData | bytes | Additional (optional) data required for removing liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsOut | uint256[] | Actual amounts of tokens received, sorted in token registration order |
removeLiquiditySingleTokenExactIn
function removeLiquiditySingleTokenExactIn(
address pool,
uint256 exactBptAmountIn,
IERC20 tokenOut,
uint256 minAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256 amountOut);
Removes liquidity from a pool via a single token, burning an exact pool token amount.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | Exact amount of pool tokens provided |
| tokenOut | IERC20 | Token used to remove liquidity |
| minAmountOut | uint256 | Minimum amount of tokens to be received |
| wethIsEth | bool | If true, outgoing WETH will be unwrapped to ETH; otherwise the Vault will send WETH tokens |
| userData | bytes | Additional (optional) data required for removing liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| amountOut | uint256 | Actual amount of tokens received |
removeLiquiditySingleTokenExactOut
function removeLiquiditySingleTokenExactOut(
address pool,
uint256 maxBptAmountIn,
IERC20 tokenOut,
uint256 exactAmountOut,
bool wethIsEth,
bytes memory userData
) external payable returns (uint256 bptAmountIn);
Removes liquidity from a pool via a single token, specifying the exact amount of tokens to receive.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxBptAmountIn | uint256 | Maximum amount of pool tokens provided |
| tokenOut | IERC20 | Token used to remove liquidity |
| exactAmountOut | uint256 | Exact amount of tokens to be received |
| wethIsEth | bool | If true, outgoing WETH will be unwrapped to ETH; otherwise the Vault will send WETH tokens |
| userData | bytes | Additional (optional) data required for removing liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountIn | uint256 | Actual amount of pool tokens burned |
removeLiquidityCustom
function removeLiquidityCustom(
address pool,
uint256 maxBptAmountIn,
uint256[] memory minAmountsOut,
bool wethIsEth,
bytes memory userData
) external returns (uint256 bptAmountIn, uint256[] memory amountsOut, bytes memory returnData);
Removes liquidity from a pool with a custom request.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxBptAmountIn | uint256 | Maximum amount of pool tokens provided |
| minAmountsOut | uint256[] | Minimum amounts of tokens to be received, sorted in token registration order |
| wethIsEth | bool | If true, outgoing WETH will be unwrapped to ETH; otherwise the Vault will send WETH tokens |
| userData | bytes | Additional (optional) data required for removing liquidity |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountIn | uint256 | Actual amount of pool tokens burned |
| amountsOut | uint256[] | Actual amounts of tokens received, sorted in token registration order |
| returnData | bytes | Arbitrary (optional) data with encoded response from the pool |
removeLiquidityRecovery
function removeLiquidityRecovery(
address pool,
uint256 exactBptAmountIn
) external returns (uint256[] memory amountsOut);
Removes liquidity proportionally, burning an exact pool token amount. Only available in Recovery Mode.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | Exact amount of pool tokens provided |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsOut | uint256[] | Actual amounts of tokens received, sorted in token registration order |
Swaps
swapSingleTokenExactIn
function swapSingleTokenExactIn(
address pool,
IERC20 tokenIn,
IERC20 tokenOut,
uint256 exactAmountIn,
uint256 minAmountOut,
uint256 deadline,
bool wethIsEth,
bytes calldata userData
) external payable returns (uint256 amountOut);
Executes a swap operation specifying an exact input token amount.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token to be swapped from |
| tokenOut | IERC20 | Token to be swapped to |
| exactAmountIn | uint256 | Exact amount of input tokens to send |
| minAmountOut | uint256 | Minimum amount of tokens to be received |
| deadline | uint256 | Deadline for the swap |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH and outgoing WETH will be unwrapped to ETH |
| userData | bytes | Additional (optional) data required for the swap |
Returns:
| Name | Type | Description |
|---|---|---|
| amountOut | uint256 | Calculated amount of output tokens to be received in exchange for the given input tokens |
swapSingleTokenExactOut
function swapSingleTokenExactOut(
address pool,
IERC20 tokenIn,
IERC20 tokenOut,
uint256 exactAmountOut,
uint256 maxAmountIn,
uint256 deadline,
bool wethIsEth,
bytes calldata userData
) external payable returns (uint256 amountIn);
Executes a swap operation specifying an exact output token amount.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token to be swapped from |
| tokenOut | IERC20 | Token to be swapped to |
| exactAmountOut | uint256 | Exact amount of output tokens to receive |
| maxAmountIn | uint256 | Maximum amount of tokens to be sent |
| deadline | uint256 | Deadline for the swap |
| wethIsEth | bool | If true, incoming ETH will be wrapped to WETH and outgoing WETH will be unwrapped to ETH |
| userData | bytes | Additional (optional) data required for the swap |
Returns:
| Name | Type | Description |
|---|---|---|
| amountIn | uint256 | Calculated amount of input tokens to be sent in exchange for the requested output tokens |
ERC4626 Buffers
initializeBuffer
function initializeBuffer(
IERC4626 wrappedToken,
uint256 amountUnderlyingRaw,
uint256 amountWrappedRaw
) external returns (uint256 issuedShares);
Adds liquidity for the first time to one of the Vault's internal ERC4626 buffers. Buffer operations will revert until the buffer is initialized.
Parameters:
| Name | Type | Description |
|---|---|---|
| wrappedToken | IERC4626 | Address of the wrapped token that implements IERC4626 |
| amountUnderlyingRaw | uint256 | Amount of underlying tokens that will be deposited into the buffer |
| amountWrappedRaw | uint256 | Amount of wrapped tokens that will be deposited into the buffer |
Returns:
| Name | Type | Description |
|---|---|---|
| issuedShares | uint256 | The amount of tokens sharesOwner has in the buffer, denominated in underlying tokens (This is the BPT of an internal ERC4626 token buffer) |
addLiquidityToBuffer
function addLiquidityToBuffer(
IERC4626 wrappedToken,
uint256 exactSharesToIssue,
) external returns (uint256 amountUnderlyingRaw, uint256 amountWrappedRaw);
Adds liquidity proportionally to a yield-bearing buffer (one of the Vault's internal ERC4626 token buffers). This limitation is necessary to avoid having multiple "wrap/unwrap" paths.
Parameters:
| Name | Type | Description |
|---|---|---|
| wrappedToken | IERC4626 | Address of the wrapped token that implements IERC4626 |
| exactSharesToIssue | uint256 | The value in underlying tokens that sharesOwner wants to add to the buffer, in underlying token decimals |
Returns:
| Name | Type | Description |
|---|---|---|
| amountUnderlyingRaw | uint256 | Amount of underlying tokens deposited into the buffer |
| amountWrappedRaw | uint256 | Amount of wrapped tokens deposited into the buffer |
Queries
queryAddLiquidityProportional
function queryAddLiquidityProportional(
address pool,
uint256 exactBptAmountOut,
bytes memory userData
) external returns (uint256[] memory amountsIn);
Queries an addLiquidityProportional operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountOut | uint256 | Exact amount of pool tokens to be received |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsIn | uint256[] | Expected amounts of tokens to add, sorted in token registration order |
queryAddLiquidityUnbalanced
function queryAddLiquidityUnbalanced(
address pool,
uint256[] memory exactAmountsIn,
bytes memory userData
) external returns (uint256 bptAmountOut);
Queries an addLiquidityUnbalanced operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactAmountsIn | uint256[] | Exact amounts of tokens to be added, sorted in token registration order |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountOut | uint256 | Expected amount of pool tokens to receive |
queryAddLiquiditySingleTokenExactOut
function queryAddLiquiditySingleTokenExactOut(
address pool,
IERC20 tokenIn,
uint256 exactBptAmountOut,
bytes memory userData
) external returns (uint256 amountIn);
Queries an addLiquiditySingleTokenExactOut operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token used to add liquidity |
| exactBptAmountOut | uint256 | Expected exact amount of pool tokens to receive |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountIn | uint256 | Expected amount of tokens to add |
queryAddLiquidityCustom
function queryAddLiquidityCustom(
address pool,
uint256[] memory maxAmountsIn,
uint256 minBptAmountOut,
bytes memory userData
) external returns (uint256[] memory amountsIn, uint256 bptAmountOut, bytes memory returnData);
Queries an addLiquidityCustom operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxAmountsIn | uint256[] | Maximum amounts of tokens to be added, sorted in token registration order |
| minBptAmountOut | uint256 | Expected minimum amount of pool tokens to receive |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsIn | uint256[] | Expected amounts of tokens to add, sorted in token registration order |
| bptAmountOut | uint256 | Expected amount of pool tokens to receive |
| returnData | bytes | Arbitrary (optional) data with encoded response from the pool |
queryRemoveLiquidityProportional
function queryRemoveLiquidityProportional(
address pool,
uint256 exactBptAmountIn,
bytes memory userData
) external returns (uint256[] memory amountsOut);
Queries a removeLiquidityProportional operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | Exact amount of pool tokens provided for the query |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsOut | uint256[] | Expected amounts of tokens to receive, sorted in token registration order |
queryRemoveLiquiditySingleTokenExactIn
function queryRemoveLiquiditySingleTokenExactIn(
address pool,
uint256 exactBptAmountIn,
IERC20 tokenOut,
bytes memory userData
) external returns (uint256 amountOut);
Queries a removeLiquiditySingleTokenExactIn operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | Exact amount of pool tokens provided for the query |
| tokenOut | IERC20 | Token used to remove liquidity |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountOut | uint256 | Expected amount of tokens to receive |
queryRemoveLiquiditySingleTokenExactOut
function queryRemoveLiquiditySingleTokenExactOut(
address pool,
IERC20 tokenOut,
uint256 exactAmountOut,
bytes memory userData
) external returns (uint256 bptAmountIn);
Queries a removeLiquiditySingleTokenExactOut operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenOut | IERC20 | Token used to remove liquidity |
| exactAmountOut | uint256 | Exact amount of tokens to receive |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountIn | uint256 | Expected amount of pool tokens to burn |
queryRemoveLiquidityCustom
function queryRemoveLiquidityCustom(
address pool,
uint256 maxBptAmountIn,
uint256[] memory minAmountsOut,
bytes memory userData
) external returns (uint256 bptAmountIn, uint256[] memory amountsOut, bytes memory returnData);
Queries a removeLiquidityCustom operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| maxBptAmountIn | maxBptAmountIn | Maximum amount of pool tokens provided |
| minAmountsOut | uint256[] | Expected minimum amounts of tokens to receive, sorted in token registration order |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| bptAmountIn | uint256 | Expected amount of pool tokens to burn |
| amountsOut | uint256[] | Expected amounts of tokens to receive, sorted in token registration order |
| returnData | bytes | Arbitrary (optional) data with encoded response from the pool |
queryRemoveLiquidityRecovery
function queryRemoveLiquidityRecovery(
address pool,
uint256 exactBptAmountIn,
) external returns (uint256[] memory amountsOut);
Queries a removeLiquidityRecovery operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| exactBptAmountIn | uint256 | MExact amount of pool tokens provided for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountsOut | uint256[] | Expected amounts of tokens to receive, sorted in token registration order |
querySwapSingleTokenExactIn
function querySwapSingleTokenExactIn(
address pool,
IERC20 tokenIn,
IERC20 tokenOut,
uint256 exactAmountIn,
bytes calldata userData
) external returns (uint256 amountCalculated);
Queries an swapSingleTokenExactIn operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token to be swapped from |
| tokenOut | IERC20 | Token to be swapped to |
| exactAmountIn | uint256 | Exact amount of input tokens to send |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountOut | uint256 | Calculated amount of output tokens to be received in exchange for the given input tokens |
querySwapSingleTokenExactOut
function querySwapSingleTokenExactOut(
address pool,
IERC20 tokenIn,
IERC20 tokenOut,
uint256 exactAmountOut,
bytes calldata userData
) external returns (uint256 amountCalculated);
Queries an swapSingleTokenExactOut operation without actually executing it.
Parameters:
| Name | Type | Description |
|---|---|---|
| pool | address | Address of the liquidity pool |
| tokenIn | IERC20 | Token to be swapped from |
| tokenOut | IERC20 | Token to be swapped to |
| exactAmountIn | uint256 | Exact amount of input tokens to receive |
| userData | bytes | Additional (optional) data required for the query |
Returns:
| Name | Type | Description |
|---|---|---|
| amountOut | uint256 | Calculated amount of input tokens to be sent in exchange for the requested output tokens |
Router common
These functions are shared between the Router, BatchRouter, and CompositeLiquidityRouter (defined in RouterCommon).
permitBatchAndCall
function permitBatchAndCall(
PermitApproval[] calldata permitBatch,
bytes[] calldata permitSignatures,
IAllowanceTransfer.PermitBatch calldata permit2Batch,
bytes calldata permit2Signature,
bytes[] calldata multicallData
) external returns (bytes[] memory results);
Permits multiple allowances and executes a batch of function calls on this contract.
Parameters:
| Name | Type | Description |
|---|---|---|
| permitBatch | PermitApproval[] calldata | An array of PermitApproval structs, each representing an ERC20 permit request |
| permitSignatures | bytes[] calldata | An array of bytes, corresponding to the permit request signature in permitBatch |
| permit2Batch | IAllowanceTransfer.PermitBatch calldata | A batch of permit2 approvals |
| permit2Signature | bytes calldata | A permit2 signature for the batch approval |
| multicallData | bytes[] calldata | An array of bytes arrays, each representing an encoded function call on this contract |
Returns:
| Name | Type | Description |
|---|---|---|
| results | bytes[] memory | Array of bytes arrays, each representing the return data from each function call executed |
multicall
function multicall(bytes[] calldata data) external returns (bytes[] memory results);
Executes a batch of function calls on this contract.
Parameters:
| Name | Type | Description |
|---|---|---|
| data | bytes[] calldata | Encoded function calls to be executed in the batch |
Returns:
| Name | Type | Description |
|---|---|---|
| results | bytes[] memory | Array of bytes arrays, each representing the return data from each function call executed |