What is DeFi? Decentralized finance explained.

Banking without the bank

When you deposit money at a bank, you're trusting the bank to hold it, lend it to other people, and give it back when you ask. When you want a loan, the bank decides whether you qualify. When you want to trade stocks, a broker executes the order. When you send money internationally, a network of correspondent banks takes a cut.

Every one of these transactions goes through an intermediary. That intermediary takes a fee, sets the rules, decides who qualifies, and operates during business hours on weekdays.

Decentralized finance — DeFi — replaces these intermediaries with software. Specifically, with self-executing code on a blockchain called smart contracts. The rules are written into the code. Transactions execute automatically. There's no bank branch, no credit check, no opening hours, no headquarters deciding who gets access.

That's the core idea. Everything else in DeFi is a variation on that theme.

What does DeFi actually do?

DeFi isn't a single product. It's an ecosystem of financial applications, each serving a function that traditional finance handles through institutions.

Lending and borrowing: In traditional finance, you apply for a loan, a bank assesses your credit history, and a human approves or rejects your application. In DeFi, you deposit crypto as collateral, and a smart contract automatically gives you a loan against it. Aave, one of the leading DeFi lending protocols, currently holds around $27 billion in total value locked — meaning $27 billion of assets are actively being lent and borrowed through its smart contracts.

Trading: Decentralised exchanges (DEXs) like Uniswap let you trade directly from your own wallet, with the exchange happening automatically through a liquidity pool — a pool of funds contributed by other users who earn a share of the trading fees in return. Uniswap alone holds around $6.8 billion in total value locked.

Earning yield: DeFi protocols pay interest to users who deposit assets. The rate is set by supply and demand within the protocol — when demand to borrow is high, lenders earn more. 

Stablecoins: DeFi gave rise to decentralised stablecoins — currencies pegged to the dollar but managed by smart contracts rather than a company. DAI, created by MakerDAO, maintains its dollar peg through an automated system of crypto collateral rather than a company holding dollars in a bank account.

Liquid staking: Ethereum requires you to lock up ETH to participate in staking and earn rewards. Protocols like Lido let you stake ETH and receive a liquid token (stETH) in return — one you can still use in other DeFi protocols while your ETH earns staking rewards. 

How does DeFi work technically?

The engine of DeFi is the smart contract — a piece of code stored on a blockchain that executes automatically when specific conditions are met.

Think of a smart contract like a vending machine. You insert the right amount, select your item, and the machine dispenses it automatically. No cashier required. The rules are built into the machine. You can't negotiate with it, bribe it, or ask it to make an exception. It does exactly what its code says.

In DeFi, smart contracts replace the role of a bank's loan officer, an exchange's order matching system, or a broker's settlement desk. When you deposit collateral into a lending protocol, the smart contract automatically calculates how much you can borrow. When you repay, it automatically releases your collateral. When a price threshold is crossed, it automatically liquidates undercollateralised positions.

Total Value Locked (TVL) is the key metric for measuring DeFi's scale. It represents the total dollar value of all assets currently deposited across DeFi protocols. Ethereum hosts the majority of DeFi activity, accounting for around 63–68% of total DeFi TVL. Solana and other Layer 1 blockchains host the remainder.

DeFi vs. traditional finance: the real differences

Permissionless access (with caveats): At the smart contract level, DeFi protocols remain open to any wallet address — there's no application, no credit check, no minimum balance. In practice, the official interfaces most people use have introduced geographic restrictions and, in some cases, light identity checks for larger transactions in response to regulatory pressure. The underlying code is still accessible without restriction, but the reality for most users is more nuanced than pure permissionlessness.

Transparency: Every transaction on a DeFi protocol is publicly visible on the blockchain. Every smart contract's code can be read by anyone. Every protocol's reserves are auditable in real time. A traditional bank's balance sheet is published quarterly, in summary form, with significant discretion over what gets disclosed.

Composability: DeFi protocols can be combined with each other freely to create new financial products. A lending protocol can plug directly into a decentralised exchange, which can connect to a yield aggregator. Developers build on top of existing protocols the way software developers build on APIs. 

No business hours: DeFi protocols run continuously on a blockchain. There's no market close, no weekend, no settlement delay. A trade executes in seconds, at any time, from anywhere.

The risks of DeFi

DeFi's openness is genuinely powerful. Its risks are equally genuine and should be understood before participating.

Smart contract risk: If a smart contract has a bug or vulnerability, attackers can exploit it. Unlike a bank, there's no deposit insurance, no regulator to intervene, and often no recourse after an exploit. DeFi protocols have collectively lost billions of dollars to smart contract exploits over the years. The best protocols undergo multiple independent security audits, but audits cannot guarantee that no vulnerabilities exist.

No safety net: Traditional finance has consumer protections built in: deposit insurance, fraud departments, chargeback mechanisms, and regulatory oversight. DeFi has none of these by default. If you send funds to the wrong address, they're gone. If a protocol is exploited, there's no claims process.

Liquidation risk: DeFi loans are overcollateralised — you must deposit more than you borrow — and if your collateral value falls below the required threshold, the protocol automatically liquidates your position. In a fast-moving market, this can happen quickly.

Complexity: Using DeFi requires managing a self-custody wallet, understanding gas fees, navigating smart contract interactions, and assessing the security of each protocol you use. The learning curve is steep, and mistakes are often irreversible.

Impermanent loss: If you provide liquidity to a DEX, you can experience impermanent loss — a reduction in the value of your position relative to simply holding the assets, caused by price movements between the two tokens in the pool.

For many people, especially those new to crypto, CeFi platforms may be the practical way to access DeFi-style products while they learn. On Nexo, you can earn up to competitive rates on your crypto through Flexible and Fixed-term Savings, borrow against your holdings with flexible repayment, and trade 100+ assets on the Nexo Exchange — the same core functions DeFi protocols provide, without needing to manage a self-custody wallet.

Where DeFi is heading

DeFi in 2026 looks substantially different from its origins in 2020. The speculative yield-farming frenzy of the early years has given way to more mature, sustainable protocols with real usage.

Three developments are reshaping the landscape. First, institutional participation is growing. Major financial firms are exploring on-chain settlement and tokenised treasury products, using DeFi infrastructure for real capital market activity. 

Second, real-world asset (RWA) integration is bridging DeFi with traditional finance — tokenised government bonds and private credit products are now being used as collateral within DeFi protocols, bringing stable, real-world yield on-chain.

The leading protocols — Lido ($27.5B TVL), Aave ($27B TVL), EigenLayer ($13B TVL), Uniswap ($6.8B TVL) — have demonstrated staying power through multiple market cycles and are increasingly being used as infrastructure rather than speculative vehicles.

Frequently asked questions

1. What is DeFi in simple terms?

DeFi — decentralized finance — is a system of financial services (lending, borrowing, trading, earning yield) that runs on blockchain smart contracts instead of banks and intermediaries.

2. What is a smart contract? 

A smart contract is self-executing code on a blockchain that runs automatically when specific conditions are met. In DeFi, smart contracts replace the role of a bank loan officer, an exchange's order matching system, or a broker's settlement process. They execute exactly as programmed, with no human intervention.

3. What is TVL in DeFi? 

TVL — Total Value Locked — is the total dollar value of all assets currently deposited in DeFi protocols. It's the primary measure of DeFi's scale. A higher TVL generally indicates more user trust and capital activity within a protocol.

4. Is DeFi safe? 

DeFi may carry genuine risks, including smart contract exploits, liquidation risk, and a complete absence of consumer protections like deposit insurance. The safest approach is to use protocols with multiple independent audits, avoid excessive leverage, and only commit funds you can afford to lose. 

5. What is the difference between DeFi and CeFi? 

DeFi (decentralized finance) is managed by smart contracts with no central authority — you hold your own funds and interact directly with protocols. CeFi (centralized finance) is managed by a company that provides financial services through a familiar interface. 

6. What is yield farming? 

Yield farming is the practice of moving assets between DeFi protocols to optimise returns — depositing funds where interest rates are highest, then moving them when better opportunities arise. It can generate strong returns but requires active management and may carry smart contract risk.

7. Can I access DeFi-style products without using DeFi directly? 

Yes. Platforms like Nexo provide earning, borrowing, and trading products that function similarly to DeFi protocols, but through a centralised interface. This is often a practical starting point for people who want the financial benefits of DeFi without the complexity of managing self-custody wallets and interacting with smart contracts.

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