Decentralized finance (often stylized as DeFi) provides financial instruments and services through smart contracts on a programmable, permissionless blockchain. This approach reduces the need for intermediaries such as brokerages, exchanges, or banks. DeFi platforms enable users to lend or borrow funds, speculate on asset price movements using derivatives, trade cryptocurrencies, insure against risks, and earn interest in savings-like accounts. The DeFi ecosystem is built on a layered architecture and highly composable building blocks.

While some applications offer high interest rates, they carry high risks. Coding errors and hacks are a common challenge in DeFi. DeFi protocols exhibit varying degrees of decentralization, with truly decentralized protocols potentially acting as neutral infrastructure, while false decentralization leaves protocols open to manipulation and fraud or to being regulated as financial intermediaries.

A core principle of DeFi is its accessibility. By operating on public blockchains, DeFi applications (commonly referred to as "dApps") enable users from across the globe to access financial services without the need for a centralized authority or compliance with traditional Know Your Customer (KYC) and Anti-Money Laundering (AML) regulations.

DeFi also introduces programmability and composability to finance. Developers can create interoperable financial products by combining different DeFi protocols like building blocks, a concept often referred to as "money Legos".

Decentralized exchanges (abbreviated DEXs) are alternative payment ecosystems that use new protocols for financial transactions. They emerged within decentralized finance (DeFi), a sector of blockchain technology and fintech.

Centralized exchanges (CEXs), DEXs and DEX aggregators are all built on a multi-layered DeFi architecture, with each layer serving a well-defined purpose. (See Figure: Multi-layered Architecture of the DeFi Stack).

While they share common components of the first four layers, such as the Settlement layer, Asset layer, Protocol layer and Application layer, DEX aggregators have an additional component or Aggregator layer, which allows them to connect and interact with other DEXs via smart contracts.

DeFi uses decentralized applications, also known as DApps, that perform financial functions on distributed ledgers called blockchains, a technology that was made popular by bitcoin. Transactions are directly made between participants, mediated by smart contract programs, rather than through a centralized intermediary. These smart contracts, or DeFi protocols, typically run using open-source software.

DApps are typically accessed through a browser extension or application. For example, MetaMask allows users to interact with Ethereum through a digital wallet. Many of these DApps can be linked to create complex financial services. Examples include lending protocols, in which stablecoin holders can lend assets to a liquidity pool, and allow others to borrow those digital assets by depositing their own collateral. The protocol is designed to automatically adjusts interest rates based on the demand for the asset.

Some DApps source external (off-chain) data, such as the price of an asset, through blockchain oracles.

The Aave protocol popularized "flash loans", which are uncollateralized loans of an arbitrary amount that are taken out and paid back within a single blockchain transaction. Exploits of DeFi platforms have used flash loans to manipulate cryptocurrency spot prices.

Decentralized exchanges (DEX) are a type of cryptocurrency exchange, which allow for either direct peer-to-peer, or Automated Market Maker (AMM) liquidity pool cryptocurrency transactions to take place without the need for an intermediary. The lack of an intermediary differentiates them from centralized exchanges (CEX).

In transactions made through decentralized exchanges, the typical third party entities which would normally oversee the security and transfer of assets (e.g. banks, stockbrokers, online payment gateways, government institutions, etc.) are substituted by a blockchain or distributed ledger. Some common methods of operation include the use of smart contracts or order book relaying –although numerous other variations are possible, with differing degrees of decentralization.

Because traders on a decentralized exchange often do not need to transfer their assets to the exchange before executing a trade, decentralized exchanges reduce the risk of theft from hacking of exchanges, but liquidity providers do need to transfer tokens to the decentralized exchange. Decentralized exchanges are also more anonymous than exchanges that implement know your customer (KYC) requirements.

As of 2018, there were signs that decentralized exchanges had been suffering from low trading volumes and reduced market liquidity. The 0x project, a protocol for building decentralized exchanges with interchangeable liquidity, attempted to solve this issue.

As of mid‑2025, weekly trading volume on decentralized exchanges (DEXs) averaged around $18.6 billion, with more than 9.7 million unique wallets interacting with DeFi protocols.