What Is DeFi? A Complete Guide to Decentralised Finance
Decentralised finance replaces banks, brokers and custodians with code. How DeFi works, what you can actually do with it, what it costs, where the risks sit, and how regulation is changing it.
Decentralised finance — DeFi — is financial infrastructure rebuilt so that the rules live in code rather than in a company. Lending, trading, saving and borrowing all still happen. What disappears is the institution in the middle deciding whether you are allowed to participate.
That single change explains most of what people find strange about DeFi, both the good and the bad. There is no account to open and no approval to wait for, but there is also nobody to call when something goes wrong.
How DeFi actually works
Three pieces do the work.
A blockchain keeps the ledger. Every balance and every transaction is recorded on a network that thousands of independent machines agree on, so no single party can quietly change history.
Smart contracts hold the logic. A lending market is a program: it accepts deposits, tracks who owns what, sets interest from supply and demand, and sells collateral when a loan becomes unsafe. Once deployed, it runs the same way for everyone.
Your wallet is the account. It holds the keys that authorise transactions. Nobody can freeze it, and nobody can recover it for you — which is the trade at the centre of all of this.
What you can do with it
Earn on idle assets
Deposit into a lending market and borrowers pay you interest. Rates float with demand rather than being set by a treasury desk. Our guide to stablecoin yield covers the conservative end of this.
Borrow without selling
Post collateral, take a loan against it, keep your exposure. This is the most-used feature in DeFi and the one with the sharpest teeth — see how LTV works and what happens at liquidation.
Provide liquidity
Supply two assets to a trading pool and collect a share of the fees. The catch has a name: impermanent loss, which is what happens when the two assets move apart in price.
Stake without locking up
Liquid staking lets you secure a network and still hold a token representing that position, so the capital stays usable elsewhere.
Farm yield
Combining the above — supplying liquidity, staking the receipt, collecting incentives — is yield farming. Returns can be high. So can the number of things that must all keep working.
What it costs
DeFi is not free, the costs are just itemised differently.
- Network fees on every transaction. On newer chains these are cents; the cost is that every adjustment is a payment.
- Protocol fees, usually a cut of interest or trading volume.
- Slippage on large trades against thin liquidity.
- Spread between supply and borrow rates, which is how lending markets fund reserves.
For small positions, fees can quietly exceed returns. That is the main reason yield farming rewards size and patience over constant tinkering.
Where the risks are
Be specific about these, because "crypto is risky" is not useful.
Smart contract risk. Code can contain bugs, and an exploited contract can lose everything in it. Audits reduce this; they do not remove it.
Oracle risk. Protocols need to know prices, and they get them from oracles. A stale or manipulated feed can trigger wrong liquidations or let someone borrow against a phantom valuation.
Liquidation risk. Collateralised borrowing works until the collateral falls. Then it is sold, often at the worst moment, usually with a penalty.
Depeg risk. Assets meant to hold a value sometimes do not. See yield-bearing stablecoins for where this bites hardest.
Key risk. Lose your keys and the funds are gone. Approve a malicious contract and they can be taken — the mechanism behind approval phishing.
DeFi and regulation
The early assumption that DeFi would sit outside regulation has not survived. In Europe, MiCA now sets rules for issuers and service providers, and DORA adds operational resilience requirements. Anywhere a business sits between users and a protocol — a front end, a custodian, an exchange — identity checks increasingly apply, which is why KYC and KYB tooling has become standard infrastructure rather than an afterthought.
The protocols themselves remain permissionless. The businesses around them mostly do not. Our MiCA guide covers what that means in practice.
How to start sensibly
- Use a self-custody wallet and back up the recovery phrase offline.
- Start with an amount you can afford to write off entirely.
- Begin with lending or stablecoin yield before anything leveraged.
- Read what the protocol actually does with your deposit.
- Review token approvals periodically and revoke what you no longer use.
The gap between DeFi and traditional finance is narrowing from both directions — see CeFi versus DeFi for where the line currently sits, and multi-chain DeFi for how this now spans several networks at once.
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