Borrow millions without collateral - if you repay in the same transaction. Understand flash loan mechanics.
advancedIntermediate45-60 minutes7 stepsPrerequisites: Solidity knowledge or flash loan tools, Understanding of DeFi protocols, Test environment
On this page
Quick Overview
1Understand Flash Loan Mechanics
2Identify Use Case
3Choose Tool or Build
4Test on Testnet
5Calculate Profitability
6Execute Flash Loan
7Verify Results
Flash loans are uncollateralized loans that must be borrowed and repaid within a single transaction. If not repaid, the entire transaction reverts as if it never happened.
How Flash Loans Work
Borrow any amount instantly
Use funds within same transaction
Repay principal + fee
If repayment fails, entire tx reverts
Common Uses:
Use Case
Description
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Arbitrage
Buy low, sell high across DEXs
Liquidations
Liquidate positions profitably
Collateral swap
Change position without unwinding
Self-liquidation
Avoid liquidation penalties
Flash Loan Providers
Aave: 0.09% fee
Balancer: No fee
Uniswap: 0.3% fee (via flash swaps)
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Step-by-Step Instructions
1
Understand Flash Loan Mechanics
Flash loans exist only within one transaction. Failure means nothing happens.
Tips
✓No collateral needed
✓Atomic: all or nothing
✓Must repay in same tx
2
Identify Use Case
Flash loans need profitable use: arbitrage, collateral swap, or liquidation.
Tips
✓Profit must exceed fees + gas
✓Arbitrage windows close quickly
3
Choose Tool or Build
Use Furucombo for no-code, DeFi Saver for position management, or code your own.
Tips
✓Furucombo: furucombo.app
✓No coding needed for basic uses
4
Test on Testnet
Always test flash loan logic on testnet first. One bug = failed transaction.
Warnings
⚠Failed tx still costs gas
⚠Test thoroughly before mainnet
5
Calculate Profitability
Include flash loan fee, gas costs, and slippage in profit calculation.
Tips
✓Aave fee: 0.09%
✓Gas on complex txs can be high
6
Execute Flash Loan
Run your flash loan transaction. Monitor for success.
Tips
✓High gas for priority
✓MEV protection recommended
7
Verify Results
Check your wallet for profit. Failed transactions show no change (except gas).