What an aggregator does
Every DEX pool quotes its own price, and the price moves as you trade into it. An aggregator reads many pools at once and builds a route: part of your trade may go through a Uniswap pool, part through Curve, part through a two-hop path via a third token. 1inch describes its Swap API as best-execution swaps built on aggregated DEX liquidity.[1]
You still trade from your own wallet. 1inch's router contract receives your tokens only for the duration of the transaction and sends the output back in the same transaction, so custody never leaves you between blocks. What you do grant is a token approval to the router, which is worth revoking if you stop using it.[1]
As of September 2026, 1inch's developer documentation lists 17 networks, including Ethereum, Arbitrum, Base, BNB Chain, Optimism, Polygon, zkSync Era and Solana, each marked as available with the full API set.[3]
The same routing engine is available to other apps. 1inch offers its Swap API to wallets and trading interfaces, so a swap button inside a third-party wallet may be using 1inch routing without the 1inch brand on screen. The documentation groups this with an Orderbook API for on-chain limit orders and RFQ and a Transaction Gateway API it describes as broadcasting with MEV protection.[1]
That matters for comparison shopping. Two wallets can show different quotes for the same trade because they use different aggregators, different fee settings or a different set of chains. The fair comparison is the final output amount after gas, not the name of the router.[1]
See also: 1inch · What is a DEX
Worked example: why splitting a trade helps
Take two Uniswap v2 style pools for ETH and USDC. Pool A holds 100 ETH and 300,000 USDC; Pool B holds 50 ETH and 150,000 USDC. Both quote 3,000 USDC per ETH and both charge 0.30%. You want to sell 10 ETH.[6]
Sending all 10 ETH to Pool A under the constant product rule returns about 27,198 USDC. Splitting the order in proportion to pool size, 6.67 ETH to A and 3.33 ETH to B, returns about 28,046 USDC in total, the same as trading into a single pool of 150 ETH. The split earns roughly 848 USDC more, about 2.8% of the trade.[6]
Two things eat into that gain. A multi-pool route uses more gas than a single swap, which matters on Ethereum mainnet and much less on a layer 2. And the quote is only valid until the next block, which is why your slippage tolerance still matters on an aggregator.
Fusion: intent-based swaps
With a classic swap you submit a transaction and pay gas yourself. With Fusion you sign an order that states what you want to receive, and resolvers, specialized professional fillers, compete to execute it. 1inch's Swap API lists these intent-based swaps next to classic transaction-based swaps.[1]
1inch's resolver documentation refers to a Dutch auction phase for Fusion orders, in which the rate changes over time until a resolver finds it worth filling. The 1inch limit order protocol supports on-chain rate functions that can implement such Dutch auctions, where the rate decreases over time.[4]
Resolvers are not anonymous bots. 1inch's resolver onboarding requires KYC or KYB checks, a compliance survey and the contract addresses a resolver will use, which are scanned against a blacklist. The same page states that whitelisting, farming and any Unicorn Power based exclusivity or eligibility mechanisms are currently disabled for Fusion and limit orders under governance proposal 1IP-89.[2]
Our reading, not a claim from 1inch's documentation: because a resolver fills your signed order in its own transaction, you do not broadcast a swap of your own to the public mempool, which is where ethereum.org says searchers watch for large DEX trades to sandwich. Whether a given fill is protected depends on how the resolver submits it.[7]
Fusion+ cross-chain swaps
Fusion+ extends the intent model across chains, for example USDC on Arbitrum for ETH on Base. It avoids a traditional bridge. According to the protocol repository, an escrow factory deploys one escrow on the source chain holding your tokens and one on the destination chain holding the resolver's tokens. Both release against a hashlock plus a set of timelocks.[5]
In plain terms: both escrows are locked to the same hashlock, so revealing the user-defined secret releases your tokens to the resolver on one chain and the resolver's tokens to you on the other. The repository's protocol design documents timelocks and rescue of funds for swaps that stall. The repository points to a Fusion+ whitepaper and a security file that lists the design's accepted risks.[5]
See also: Crypto bridges
Limit orders and fees
The 1inch Limit Order Protocol lets you sign an order off-chain, using the EIP-712 format, that anyone can fill on-chain when the conditions are met. Options include partial fills, expiration dates, a private taker address, stop-loss or take-profit conditions, and support for ERC-20, ERC-721 and ERC-1155 tokens.[4]
1inch's resolver onboarding page lists fees of 5 basis points for stable or pegged pairs and 30 basis points for other pairs. Classic swaps also pass through the fees of the underlying pools, plus network gas.[2]
Orders can also carry a nonce or epoch for easy cancellation and can ask for WETH to be unwrapped to ETH before or after the trade. Because orders are signed off-chain, creating one costs no gas; the filler pays gas when executing it.[4]
| Order type | Who submits the transaction | Main use |
|---|---|---|
| Classic Swap | You, paying gas | Immediate swap routed across DEXs |
| Fusion | A resolver | Intent swap filled through a Dutch auction |
| Fusion+ | A resolver on both chains | Cross-chain swap using escrows |
| Limit order | Whoever fills it | Swap at your price or better, later |
Alternatives and when to use them
1inch competes with other aggregators and intent-based systems, such as ParaSwap and CowSwap, each with its own routing and settlement design. For a single liquid pair, going direct to one DEX can be just as good and simpler to verify.
On any of them, run the same check: output after gas, slippage setting, and the contract your wallet asks you to approve.
See also: 1inch alternatives · ParaSwap · CowSwap · Jupiter · Uniswap
Risks to keep in mind
An aggregator adds a layer, and every layer has contract risk. The limit order protocol repository itself warns that its master branch is work in progress, unaudited and may contain severe security issues, and points users to tagged releases that went through security audits. The warning is a good reminder that version matters.[4]
Approvals are the everyday risk. A classic swap needs your approval for the router, and the limit order protocol supports approve, permit and permit2 schemes. An approval stays in place until you revoke it, and a signed permit until it is used or expires, so a phishing site that imitates the 1inch interface can ask for the same signature a real swap would.[4]
Cross-chain swaps carry timing risk. Fusion+ escrows use timelocks so funds can be recovered if a swap stalls, but recovery happens only after the timelock passes. The repository's security file documents the accepted risks of that design, and it is worth reading before moving large amounts across chains.[5]
Finally, route quality depends on data at the moment of quoting. A route that looked best can return less if pools move before the transaction lands, which is why slippage settings apply to aggregators exactly as they do to single DEXs.[7]
The bottom line
Use 1inch when a trade is large enough that price impact on one pool would cost more than the extra gas of a split route, which you can see by comparing a direct DEX quote's price impact with the aggregator's after-gas output. If sandwich risk worries you, a Fusion order, where a resolver submits the transaction, is worth comparing with a classic swap. For a small swap of a major pair on mainnet, compare the after-gas output with a direct DEX quote before assuming the aggregator wins.
Educational content, not financial advice. Crypto assets are volatile; do your own research.