SwapRouter vs SwapRouter02 vs UniversalRouter

Uniswap has shipped three generations of swap routers. Each builds on the last, adding protocol support and improving gas efficiency and approval UX.

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
• Live and unchanged since the V3 launch in 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#

1
2

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#

1
2
3

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