Uniswap has shipped three generations of swap routers. Each builds on the last, adding protocol support and improving gas efficiency and approval UX. This page compares all three to help you choose the right one.

At a Glance#

SwapRouter (V3)#

The original V3 swap router. It exposes a clean Solidity interface (ISwapRouter) with four functions: exactInputSingle, exactInput, exactOutputSingle, and exactOutput. See the ISwapRouter guide for full details.

Strengths:

• Simplest to understand and integrate
• Battle-tested since V3 launch (May 2021)
• Extensive documentation and examples

Limitations:

• V3 pools only — no V2 fallback
• Requires a separate approve tx per token per contract
• No native ETH support — you must wrap/unwrap WETH manually
• No batching — each swap is a separate call

Canonical address (most chains): 0xE592427A0AEce92De3Edee1F18E0157C05861564

SwapRouter02#

Combines V2 and V3 routing into a single contract. Adds multicall() for batching and built-in ETH wrapping.

Strengths:

• Routes through both V2 and V3 pools — finds better prices when V2 has deeper liquidity for a pair
• multicall() lets you batch multiple swaps or swap + unwrap in a single tx
• Built-in unwrapWETH9 and refundETH convenience functions
• Familiar Solidity interface — similar parameter structs to SwapRouter

Limitations:

• Still uses the traditional approve model — users must send a separate approval tx per token
• No V4 pool support
• No command-based flexibility — you’re limited to the functions the contract exposes

Canonical address (Ethereum mainnet): 0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45

UniversalRouter#

The current recommended entry point. Uses a command-based architecture where you encode an array of commands (bytes) and inputs, then call execute(). Integrates with Permit2 for gasless, signature-based approvals.

Strengths:

• Supports V2, V3, V4, and NFT purchases in a single transaction
• Permit2 approvals — users approve the Permit2 contract once, then sign off-chain permits per swap (no per-router approval tx)
• Best gas efficiency — batches multiple operations, uses a single transferFrom per token
• Flexible command system — compose arbitrary sequences of swaps, wraps, transfers, and permits
• SWEEP and PAY_PORTION commands enable fee collection and token distribution without wrapper contracts

Limitations:

• Steeper learning curve — no human-readable function signatures; you encode commands as byte arrays
• Debugging is harder — reverts surface as command indices rather than named function errors
• Requires understanding the Permit2 flow (approve Permit2 once, then sign typed-data permits)
• Fewer Solidity examples in the wild compared to SwapRouter

Canonical address (Ethereum mainnet): 0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD

Approval Flow Comparison#

SwapRouter / SwapRouter02#

User → approve(router, amount) → ERC-20 token   [on-chain tx per token]
User → swap(...)               → Router          [on-chain tx]

Each new router contract requires a fresh approval. If you switch routers, users pay for new approval transactions.

UniversalRouter + Permit2#

User → approve(permit2, type(uint256).max) → ERC-20 token   [one-time on-chain tx per token]
User → sign EIP-712 permit                                   [off-chain, free]
User → execute(commands, inputs)           → UniversalRouter [on-chain tx with permit bundled]

Users approve Permit2 once per token. After that, each swap only needs an off-chain signature — no extra approval transactions even when Uniswap deploys new router versions.

Which Should You Use?#

Further Reading#

• UniversalRouter Overview
• Permit2 Overview
• SwapRouter02 Source
• ISwapRouter Guide — detailed walkthrough of the original V3 router
• Uniswap Deployment Addresses