How Does DeFi Work?

DeFi, short for decentralized finance, is the umbrella term for apps that provide financial services such as trading, lending, borrowing and earning yield through smart contracts running on a blockchain, with no bank or centralized exchange in between. You don’t open an account or verify your identity; you connect your own wallet and transact directly with the contract.

Most DeFi activity happens on Ethereum and its Layer 2 networks, with large ecosystems on Solana, BNB Smart Chain and Avalanche as well. Uniswap, Aave, Curve and Lido are among the best-known DeFi apps.

How does DeFi work?

In traditional finance, an institution carries out your transaction: you instruct the bank, and the bank updates its records. In DeFi, that role is played by smart contracts whose rules are written in code and deployed on the blockchain. You sign a transaction with your wallet; if it meets the contract’s rules, the contract executes it automatically and the result is recorded on-chain for anyone to see.

In a swap, for example, the contract prices the trade from the token balances in its pool, takes one token from you and sends you the other. No employee approves it, there are no business hours and no account limits. The flip side is that there’s no customer service to reverse a mistake.

Some DeFi apps need outside data such as asset prices. That data is brought on-chain by services called oracles, with Chainlink the most widely used provider.

DeFi vs centralized exchanges

• Custody: on a centralized exchange, your assets sit in the exchange’s wallets; in DeFi, they stay in your own wallet and only move to a contract when you transact.
• Access: exchanges require sign-up and identity checks; most DeFi apps only need a wallet connection.
• Transparency: DeFi contract code and pool balances can be inspected on-chain by anyone.
• Responsibility: in DeFi, no institution will make you whole after a wrong network, a fake token or a malicious signature.

What is DeFi used for?

• Trading: swapping tokens without an intermediary on decentralized exchanges (DEXs) such as Uniswap and Curve.
• Lending and borrowing: earning interest by supplying assets to protocols like Aave and Compound, or borrowing against collateral.
• Providing liquidity: depositing tokens into DEX pools to earn a share of trading fees.
• Liquid staking: staking ETH through protocols like Lido and receiving a tradable token in return.
• Stablecoins: crypto-collateralized stablecoins such as DAI are created through DeFi contracts.

Where does DeFi yield come from?

When a DeFi app advertises a high return, the first question to ask is who is paying it. Sustainable yield usually comes from three places: interest paid by borrowers, fees paid by traders and staking rewards.

Many protocols also hand out their own tokens as incentives. The eye-catching APY figures these create tend to shrink fast when the token’s price falls or the emissions end. It’s worth separating how much of a yield comes from real revenue and how much from incentives.

The main risks of DeFi

• Smart contract risk: a bug in the code can let attackers drain funds. Audits reduce this risk but don’t eliminate it.
• Oracle and price manipulation: bad price data can trigger unfair liquidations or let a pool be emptied.
• Bridge risk: cross-chain bridges have been the target of some of the largest hacks in crypto history.
• Governance and admin keys: in many protocols, a team or multisig can upgrade the contracts.
• User-side risks: fake sites, unlimited token approvals and borrowing without understanding liquidation.

It’s tempting to read a high TVL (total value locked) as a sign of safety. TVL only measures how much money has been deposited, and a large TVL can also make a protocol a more attractive target.

Example: how a DeFi swap actually happens

Say you hold USDC and want ETH. You open a DEX and connect your wallet. If it’s your first time using USDC there, your wallet first asks you to approve the DEX contract to spend your USDC; that’s a separate transaction with a small gas fee.

Next, the swap screen shows the estimated ETH you’ll receive, the price impact and the minimum amount you’ll accept (your slippage tolerance). When you confirm, the contract prices the trade from the pool’s USDC-to-ETH ratio and sends the ETH to your wallet in the same transaction. If the price moves beyond your limit, the transaction fails and your tokens stay put; only the gas is spent.

How is borrowing possible without a credit check?

With no identity or credit score in DeFi, loans are overcollateralized. A hypothetical example: you deposit $1,000 of ETH as collateral and borrow $600 in stablecoins against it. If the collateral’s value falls below a set threshold relative to the loan, the protocol automatically sells part of the collateral to repay the debt. This is called liquidation.

This design removes the risk of borrowers defaulting from the protocol’s point of view, and shifts the risk of a falling collateral price onto the borrower.

Is DeFi safe?

DeFi doesn’t ask you to trust a central institution; instead, you’re trusting code, oracles and your own discipline. Protocols that have run for years, passed multiple audits and avoided major exploits are generally seen as more reliable. Even so, starting with an amount you can afford to lose and spreading funds across protocols limits the damage any single failure can do.

How to get started with DeFi

1. Set up a self-custody wallet and store the recovery phrase securely.
2. Move the network’s gas token (ETH on Ethereum, for example) and the token you want to use into the wallet.
3. Reach the app through a bookmark or a trusted source, not a search ad.
4. Connect your wallet and start with a small amount. Check the token and amount on the approval screen, and the expected outcome on the transaction screen.
5. Afterwards, keep an eye on your position and approvals, and if you’ve borrowed, monitor your collateral ratio regularly.

Sources

• Ethereum: Decentralized Finance
• Ethereum: External Data Sources (Oracles)
• Ethereum: Smart Contract Security