DeFi Lending Protocols Explained
Decentralized lending protocols let anyone in the world borrow crypto or earn interest on deposits — with no bank, no credit check, and no paperwork. Just a crypto wallet and collateral.
This is one of the most widely used applications in all of DeFi, and understanding it is essential to navigating the space.
How Traditional Lending Works
In traditional finance:
- You apply for a loan
- The bank checks your credit score and income
- The bank approves or denies based on your trustworthiness
- You repay with interest over time
The bank is the trusted intermediary. It carries the risk of default.
How DeFi Lending Works
DeFi replaces the bank with a smart contract:
- You deposit collateral (e.g., ETH)
- The smart contract automatically allows you to borrow up to a percentage of your collateral's value
- If your collateral falls below the required ratio, the contract automatically liquidates it
- No trust in any person or institution required — the code enforces everything
Why DeFi Loans Are Overcollateralized
Traditional loans are based on trust and credit history. DeFi has neither — it's pseudonymous. So instead, DeFi loans require overcollateralization: you must deposit more than you borrow.
Typical collateral ratios:
- ETH on Aave: Borrow up to 80% of your deposited ETH value
- BTC on Compound: Borrow up to 70% of your deposited BTC value
Example: Deposit $10,000 of ETH → borrow up to $8,000 of USDC
This protects lenders even if the borrower never repays — the collateral covers the loan.
The Major Lending Protocols
Aave
The largest DeFi lending protocol by total value locked. Supports dozens of assets, multiple networks, and innovative features like flash loans and interest rate switching.
Compound
One of the pioneers of DeFi lending. Simpler interface, strong security track record. Introduced the concept of distributing governance tokens (COMP) to users.
MakerDAO
A unique lending model where you borrow DAI (a stablecoin) against your ETH collateral. The DAI is newly minted by the protocol when you borrow and burned when you repay.
Morpho
A newer protocol that optimizes interest rates by matching lenders and borrowers peer-to-peer on top of Aave and Compound.
Supply and Borrow Rates
Interest rates in DeFi are determined by utilization rate — how much of a pool's deposits are currently borrowed:
- Low utilization → low borrow rates (capital is plentiful) → lower supply rates
- High utilization → high borrow rates (capital is scarce) → higher supply rates
This creates a self-balancing market: high rates attract more depositors and discourage borrowers, bringing utilization back down.
Liquidation: The Core Risk for Borrowers
If the value of your collateral falls and your health factor (collateral ratio) drops below the protocol's minimum, your position gets liquidated:
- Liquidators (bots watching the blockchain) repay part of your debt
- In return, they receive your collateral at a discount (typically 5–15%)
- This happens automatically — no warning, no grace period
How to avoid liquidation:
- Borrow conservatively — leave a significant buffer
- Monitor your health factor actively
- Add more collateral if prices fall
- Set up price alerts
Flash Loans: Uncollateralized Borrowing
Flash loans are a uniquely DeFi primitive: loans with no collateral, as long as they're borrowed and repaid within a single transaction block.
This sounds impossible — but because the blockchain processes everything atomically, if the loan isn't repaid within the transaction, the entire transaction reverts as if it never happened.
Use cases:
- Arbitrage: Borrow, exploit a price difference across DEXs, repay, keep profit
- Collateral swaps: Replace your collateral type in one transaction
- Liquidations: Fund a liquidation without needing capital upfront
Flash loans are almost exclusively used by developers and sophisticated traders.
Why Borrow If You Have Crypto?
This is the most common beginner question. Reasons to borrow:
- Avoid a taxable event: Selling crypto is taxable. Borrowing against it isn't (in most jurisdictions — check your local rules)
- Maintain exposure: Keep your ETH position while accessing liquidity
- Leverage: Borrow, buy more ETH, deposit that as collateral, borrow again (leveraged loop — very risky)
- Arbitrage: Access capital quickly for profit opportunities
Continue Learning
- Liquidity Pools — where the deposited capital comes from
- Stablecoins — the most borrowed asset in DeFi
- Yield Farming — using lending positions in broader strategies
- DeFi Risks — liquidation, smart contract bugs, and more
For a full exploration of DeFi lending and borrowing, read Understanding DeFi from the Mastering Crypto series.