Under the hood, a DEX aggregator relies on a routing engine, often called a smart order router, that scans multiple decentralized exchanges, order-book style venues, and even private market makers before a trade is submitted. Rather than sending an entire order to one venue, the router can break it into smaller pieces and fill each piece from a different pool, since a large trade against a single liquidity pool tends to move the price against the trader. This splitting is what lets aggregators consistently beat manual swaps on both price and slippage, especially for sizeable orders.

Some newer aggregators, such as 1inch's Fusion mode, go a step further with an intent-based model: instead of broadcasting a transaction directly, the user signs an off-chain order that competing professional resolvers fill through a timed auction, which also helps shield the trade from front-running and other forms of MEV. Cross-chain aggregators extend the same idea across blockchains, letting a user swap an asset native to one network for a token on another without manually bridging first.

Because an aggregator routes through several underlying protocols within a single transaction, its own contract and every pool it touches becomes part of the trust surface: a bug or exploit in any connected automated market maker can affect the trade. Routing across multiple pools also adds computation, so gas costs can run higher than a simple single-exchange swap.