# DeFi arbitrage: why prices converge and differences can remain Arbitrage combines purchases and sales across markets to exploit a price difference. In DeFi it can move AMM inventory toward prices elsewhere. A displayed spread is not a guaranteed profit: trade impact, fees, execution order and the ability to complete every leg all affect the result. Evidence: [Maximal extractable value](https://ethereum.org/developers/docs/mev/); [Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing) Canonical: https://degreesofsatoshi.com/encyclopedia/defi-arbitrage/ Published: 2026-10-02 Substantively modified: 2026-10-02 Independently verified by an automated reviewer: 2026-10-02T15:08:18.373Z AI-assisted research and drafting with a separate automated source-verification pass; no external expert or named human review is implied. ## Key facts - **Price link:** Arbitrage can bring pool prices closer to external markets. ([Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing)) - **Ordering:** Competition for transaction order affects opportunities. ([Maximal extractable value](https://ethereum.org/developers/docs/mev/)) - **Atomic borrowing:** A pure flash loan must settle within its transaction. ([Aave V3 flash loans](https://aave.com/docs/aave-v3/guides/flash-loans)) ## A spread is the start of a calculation Suppose a tiny purchase of A costs 100 B on one venue and a tiny sale pays 102 B on another. The two-unit difference is an indicative spread. Buying a substantial quantity can raise the purchase rate while selling it can lower the sale rate. A complete calculation uses executable amounts, both venues’ fees, gas and any borrowing cost. It also accounts for token identity: similarly named bridged or wrapped assets are not automatically interchangeable claims. Evidence: [Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing) ## One transaction can combine several legs On a compatible chain, contract calls can attempt a purchase, sale and repayment within one transaction. If a required condition fails and the transaction reverts, its state changes are rolled back. Gas already used by an included attempt still has a cost. A pure flash loan supplies temporary capital under that atomic condition. It does not guarantee that a profitable sequence exists. Moving funds across independent chains or a centralized venue can introduce timing and custody steps outside the atomic transaction. Evidence: [Aave V3 flash loans](https://aave.com/docs/aave-v3/guides/flash-loans); [EIP-140: REVERT instruction](https://eips.ethereum.org/EIPS/eip-140) ## Why a gap may disappear before execution Other searchers can spot the same opportunity and compete for inclusion or a favorable order. The price difference visible at a previous block may disappear before a submitted transaction executes. Arbitrage supplies a mechanism connecting prices rather than a promise that prices are always equal. Fees, inventory limits and execution constraints can maintain differences. When citing a spread, record its venues, assets and observation time. Evidence: [Maximal extractable value](https://ethereum.org/developers/docs/mev/); [Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing) ## Questions ### Is a visible price difference free money? No. The useful comparison is the completed trade after all legs, costs and price impact. Competitors and changing state can remove the opportunity before execution. Evidence: [Maximal extractable value](https://ethereum.org/developers/docs/mev/); [Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing) ## Claims and scope ### defi-arbitrage-quick-answer Arbitrage combines purchases and sales across markets to exploit a price difference. In DeFi it can move AMM inventory toward prices elsewhere. A displayed spread is not a guaranteed profit: trade impact, fees, execution order and the ability to complete every leg all affect the result. Scope: {"collection":"defi","dataAsOf":null,"blockHeight":null} ### defi-arbitrage-fact-price-link Price link: Arbitrage can bring pool prices closer to external markets. Scope: {"collection":"defi","dataAsOf":null,"blockHeight":null} ### defi-arbitrage-fact-ordering Ordering: Competition for transaction order affects opportunities. Scope: {"collection":"defi","dataAsOf":null,"blockHeight":null} ### defi-arbitrage-fact-atomic-borrowing Atomic borrowing: A pure flash loan must settle within its transaction. Scope: {"collection":"defi","dataAsOf":null,"blockHeight":null} ## Sources - [Maximal extractable value](https://ethereum.org/developers/docs/mev/) — ethereum.org contributors. Transaction ordering, arbitrage, liquidation and sandwich mechanisms. Locator: MEV extraction; Examples of MEV. Retrieved: 2026-10-02. - [Uniswap v2 pricing](https://developers.uniswap.org/docs/protocols/v2/concepts/pricing) — Uniswap. Reserve-dependent quotes, trade bounds and external price observations. Locator: Pricing Trades; Exact Input; Exact Output. Retrieved: 2026-10-02. - [Aave V3 flash loans](https://aave.com/docs/aave-v3/guides/flash-loans) — Aave. Atomic repayment, receiver callbacks and distinct debt-opening options. Locator: Overview; Execution Flow; Flash loan fee. Retrieved: 2026-10-02. - [EIP-140: REVERT instruction](https://eips.ethereum.org/EIPS/eip-140) — Ethereum Improvement Proposals. Reverting rolls back state but does not refund work already executed; unused gas is not all consumed. Locator: Specification; Test Cases. Retrieved: 2026-10-02. ## Revision history - 2026-10-02: First publication after primary-source research and independent automated verification. - 2026-10-02: Before first publication, independent review checked and revised: sections, sources. Read MEV arbitrage/order competition, v2 reserve pricing and Aave atomic flash-loan execution. Spread is correctly indicative until all costs and executable quantities are included. Added EIP-140 support for state rollback and consumed-gas qualification. Cross-chain/custodial legs are excluded from a single-chain atomic guarantee. ## Cite this entry Degrees of Satoshi editorial project. “DeFi arbitrage: why prices converge and differences can remain.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/defi-arbitrage/