Swap: Inside Uniswap V2’s Core Operation

Three posts in. We've established what AMMs are and how the constant product formula works, mapped out the contract architecture, and walked through how liquidity gets added to a pool. If you haven't read those, this post will still make sense in isolation, but some things will click harder with the context. This is the one most people care about. Everything else in Uniswap exists to support this. The swap is what users actually come for, and it's where the x · y = k formula stops being a concept on a whiteboard and starts being enforced on-chain, in real time, with real money. The full path, same as always: User → Router → Pair → User What you're actually choosing when you swap Before getting into the mechanics, there's a design decision at the Router level worth understanding because it shapes everything downstream. When you want to swap tokens, you have two fundamentally different ways to express what you want: "I have exactly 100 USDC and I want as much ETH as possible for it." Thi