Decentralised finance — DeFi — is the attempt to rebuild financial services as open software. Instead of a bank deciding whether you can borrow, a smart contract does. Instead of a stock exchange matching orders, a pool of tokens and a formula set the price. Anyone with a wallet and an internet connection can use it, and anyone can read the code.
That openness is DeFi’s great strength and its great danger. This guide explains the building blocks, sizes the market with current data, and is honest about what can go wrong.
What makes something “DeFi”?
A financial application usually qualifies as DeFi if it is:
- Non-custodial — you keep control of your assets in your own wallet until the moment you interact with the protocol.
- Run by smart contracts — programs deployed on a blockchain (most often Ethereum) that execute automatically when conditions are met.
- Permissionless — there is no sign-up form, no account approval, and generally no KYC at the protocol level.
- Composable — protocols can plug into each other like Lego bricks. A token you receive from one can be used as collateral in another.
Compare that with a crypto exchange app. When you buy bitcoin on a centralised exchange, the exchange holds it for you: that is CeFi, not DeFi.
How big is DeFi right now?
The standard yardstick is Total Value Locked (TVL) — the value of assets deposited in DeFi smart contracts. According to DefiLlama, DeFi TVL stood at about $92.6 billion in mid-October 2026, down about 3.7% over the prior week. Earlier in the month, on 2 October, DefiLlama’s API recorded $95.8 billion (WealthyBud, citing DefiLlama).
Where that value sits, per DefiLlama’s chain rankings:
| Chain | DeFi TVL (mid-Oct 2026) |
|---|---|
| Ethereum | ~$51.8B |
| Solana | ~$6.3B |
| Base | ~$6.3B |
| Tron | ~$5.6B |
| BNB Chain | ~$5.6B |
| Bitcoin | ~$4.5B |
Ethereum alone holds more than half of all DeFi value. The largest individual protocols on DefiLlama’s rankings were Lido (liquid staking, about $24.8 billion) and Aave (lending, about $18.7 billion).
A caution on interpretation: TVL rises and falls with token prices, so it is partly a price index, not just a measure of usage. And TVL is not the same as “DeFi market cap” — that measures the value of DeFi tokens, a different number entirely (WealthyBud explains the distinction well).
The building blocks
1. Stablecoins: DeFi’s base currency
Most DeFi activity is denominated in stablecoins — tokens designed to track a currency, usually the US dollar. Some are backed by cash and treasury bills held by a company; others are backed by crypto collateral locked in smart contracts. Total stablecoin supply was roughly $305 billion through Q3 2026 (Nexus One), and DefiLlama shows about $146 billion of stablecoins on Ethereum alone (DefiLlama chains).
Stablecoins are why DeFi is usable at all: you can lend, borrow and trade without your unit of account swinging 5% in an afternoon.
2. Decentralised exchanges (DEXs) and AMMs
Traditional exchanges use an order book — buyers and sellers post prices and a matching engine pairs them. Most DEXs instead use an automated market maker (AMM).
In the classic design popularised by Uniswap, a pool holds two tokens, and trades must keep the product of the two balances constant (x × y = k). Buy token A and the pool has less A and more B, so A’s price rises automatically (Uniswap docs). Anyone can become a liquidity provider by depositing both tokens, earning a share of trading fees.
The catch for liquidity providers is impermanent loss: if the two tokens’ prices diverge sharply, you can end up worse off than if you had simply held them.
3. Lending and borrowing
Protocols like Aave let users deposit assets to earn interest, and let others borrow against collateral. Because there is no credit check, loans are over-collateralised: to borrow $1,000 of stablecoins you might need to lock $1,500 or more of ETH.
If your collateral’s value falls below a threshold, the protocol automatically liquidates it — sells part of it to repay the loan — usually with a penalty. That mechanism keeps lenders whole, but it makes borrowers vulnerable to sudden price drops.
Interest rates float algorithmically based on supply and demand for each asset: when a pool is heavily borrowed, rates rise to attract more deposits.
4. Liquid staking
Ethereum is secured by validators who stake ETH. Liquid staking protocols such as Lido let you stake and receive a token representing your staked ETH plus rewards, which you can then use elsewhere in DeFi. Its size — the largest protocol by TVL on DefiLlama — shows how central staking yield has become.
5. Derivatives, yield aggregators and more
On top of these primitives sit perpetual futures exchanges, options protocols, and “vaults” that automatically move funds between strategies. Each extra layer adds yield opportunities — and additional points of failure.
Why people use DeFi
- Access. No minimum balance, no account approval, open 24/7.
- Transparency. Reserves, loans and trades are visible on-chain in real time — unlike a bank’s balance sheet.
- Self-custody. You aren’t exposed to an exchange freezing withdrawals or going bust.
- Programmability. Developers can build new products on existing protocols without asking permission.
The risks — read this part twice
DeFi removes some risks (an intermediary running off with your money) and introduces others.
- Smart-contract bugs. Code is law, including buggy code. Exploits have drained hundreds of millions from protocols over the years. Audits reduce, but do not eliminate, this risk.
- Oracle manipulation. Protocols rely on price feeds (“oracles”). If an attacker can distort a feed, they can trigger unfair liquidations or borrow against inflated collateral.
- Liquidation risk. A fast market drop can liquidate leveraged positions in minutes.
- Stablecoin de-pegs. A stablecoin is only as good as its backing and design. If it loses its peg, everything built on it wobbles.
- Governance and admin keys. Many “decentralised” protocols can still be upgraded by a small group holding admin keys or governance tokens.
- Composability contagion. Because protocols stack, a failure in one can cascade to others.
- Phishing and wallet drains. Most retail losses come from signing a malicious transaction, not from protocol hacks. Never approve transactions you don’t understand, and revoke unused token approvals.
- Illicit finance concerns. The US Treasury’s 2023 DeFi illicit finance risk assessment found that illicit actors use DeFi services, partly because many protocols lack AML controls — a key reason regulators are circling.
DeFi and Indian users
Two points specific to India:
- Tax still applies. Gains from DeFi trades and swaps are generally income from the transfer of a Virtual Digital Asset, taxed at a flat 30% with no loss set-off. Because many DeFi transactions happen outside Indian exchanges, the 1% TDS may not be deducted automatically — but your reporting obligation remains. See our India regulation & tax explainer.
- Regulatory posture. The RBI has argued for keeping regulated institutions insulated from crypto and privately issued stablecoins (Economic Times). DeFi lives entirely outside that regulated perimeter, with no investor protection to fall back on.
How to explore DeFi safely
- Start by reading, not depositing. Browse DefiLlama to see protocols, chains and TVL trends.
- Use a separate “hot” wallet with only what you’re prepared to lose.
- Prefer battle-tested protocols with long track records, multiple audits and large, diversified TVL.
- Avoid leverage until you deeply understand liquidation mechanics.
- Be sceptical of high yields. If you can’t identify where the yield comes from, you may be the yield.
- Record every transaction for tax purposes.
The bottom line
DeFi is real infrastructure: tens of billions of dollars of assets are lent, borrowed and traded through open-source contracts every day. It offers transparency and access that traditional finance can’t match. But it shifts responsibility entirely onto the user, with no helpline, no deposit insurance and no regulator to appeal to. Understand the mechanics first; the yield can wait.
Data as of mid-October 2026 from the linked sources. TVL figures move daily. This is not financial advice.