What Is a Flash Loan?

Zac McClure
ByZac McClure, MBAReviewed byAlex MilesUpdated on January 23, 2024 · minute read
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  • Flash loans are quick, collateral-free loans in decentralized finance (DeFi), ideal for traders seizing market opportunities, including arbitrage.

  • The best crypto flash loan platforms available today include Aave and Uniswap, which enable complex financial operations without the hassles associated with traditional lending.

How do flash loans work?

In the rapidly evolving landscape of decentralized finance (DeFi), flash loans emerge as a distinctive form of uncollateralized lending, gaining popularity across Ethereum-based protocols. Unlike traditional loans, flash loans employ smart contracts—blockchain-enabled tools dictating that funds only change hands when specific conditions are met. 

The crucial rule for flash loans is that borrowers must repay the loan within the same transaction block, or the smart contract automatically reverses the transaction.

Unique properties of flash loans:

Smart contracts
Flash loans utilize smart contracts, ensuring loan repayment within the same transaction.

Unsecured loan
Unlike traditional loans, crypto flash loans do not require collateral. Repayment is immediate.

Crypto flash loans are executed instantly within a few seconds, requiring borrowers to perform swift trades with the loaned capital before the transaction concludes.

What are flash loans used for?

Flash loans introduce a novel and impactful tool to the financial world, primarily favored for arbitrage and quick trades that were previously unattainable. While these loans have faced criticism for exploiting vulnerabilities in DeFi protocols, advocates argue for their innovation in facilitating arbitrage opportunities and market maneuvers. Aave pioneered the concept of flash loans in early 2020.

Best flash loan platforms in 2024

Explore the best crypto loan platforms facilitating flash loans in the space.


Best crypto flash loan for diverse digital asset lending

Aave is a pioneer in decentralized finance (DeFi), originally launching as ETHlend in 2017. The platform offers an open-source liquidity protocol that enables users to lend and borrow various digital assets without the need for a central authority. Here's an overview of Aave's features, pros, and cons.

-  Pros & Cons


  • Large Lending Pool: Aave boasts a substantial lending pool for digital assets, providing users with ample choices.

  • Feature-Rich: Offers a comprehensive range of features for both lending and borrowing, enhancing user flexibility.

  • Stable Interest Rates: Maintains stable interest rates for select assets, contributing to a more predictable borrowing environment.

  • Flash Loans (KYC Free): Allows users to access flash loans without the need for Know Your Customer (KYC) verification, facilitating quick transactions.


  • User-Friendly Challenges: Aave's interface is noted to be less user-friendly compared to some other platforms, potentially posing a barrier for newcomers.

  • Security Concerns: Flash loans have been exploited by hackers in the past, raising security concerns among users.

-  Why our experts picked it

Aave's large lending pool and diverse features make it a compelling choice for users seeking flexibility in digital asset lending. Despite some user interface challenges, Aave's continuous development and commitment to security make it a standout in the decentralized lending space.

Equalizer Finance

Best crypto flash loan for next-gen flash lending and diverse use cases

Equalizer Finance positions itself as a next-generation decentralized flash lending marketplace, connecting borrowers and liquidity providers in the DeFi space.

-  Pros & Cons


  • Dynamic Fees: Flash loan fees are adaptable, determined by governance votes or algorithmic approaches, striking a balance between attracting liquidity providers and being accessible to arbitrageurs.

  • Incentive Scheme: Offers an exclusive incentive scheme for consistent liquidity providers, encouraging continuous staking even during market volatility.

  • Scalability: Boasts infrastructure scalability, ensuring high transaction speeds for efficient flash lending operations.

  • Token Variety: Allows users to choose from an unlimited number of tokens, offering flexibility and choice on the platform.

  • Focus on Flash Loans: Equalizer Finance excels in providing flexible and adaptable flash loan services, catering to market changes.


  • No Mobile App: Currently lacks a mobile application, potentially limiting accessibility for users who prefer mobile platforms.

-  Why our experts picked it

Equalizer Finance excels in several key areas that make it a compelling choice in the decentralized finance landscape. Its dynamic fee structure, adaptive incentive schemes, and scalability contribute to a seamless flash lending experience.


Best crypto flash loan platform for complex DeFi

Furucombo empowers users to execute advanced decentralized finance (DeFi) strategies seamlessly. From arbitrage trades to self-hedging, the platform offers a range of functionalities. Here's a breakdown of the pros and cons of using Furucombo.

-  Pros & Cons


  • Versatility: Furucombo supports a wide array of DeFi strategies, including arbitrage trades, collateral swaps, self-hedging, and more, providing users with diverse options.

  • Multi-Chain Support: Furucombo is compatible with various blockchain networks, including Ethereum and Polygon, enhancing accessibility for users on different chains.

  • Efficiency Through Flash Loans: The integration of flash loans allows for instant and almost simultaneous execution of complex transactions, saving time and gas fees.

  • Innovative Features: Furucombo introduces innovative features like self-liquidation and debt refinancing, showcasing its commitment to staying at the forefront of DeFi developments.


  • Complex to Use: Will be complex for those new to crypto and DeFi.

  • Limited Furucombo Blocks on Polygon: While Furucombo supports Polygon, it offers fewer blocks compared to Ethereum, potentially limiting the range of available tools for users on the Polygon network.

  • Dependence on User Finding Arbitrage Opportunities: Furucombo doesn't find arbitrage opportunities for users; they need to identify these opportunities independently, which may require additional research and effort.

  • Potential for Short-Lived Arbitrage Opportunities: The effectiveness of arbitrage opportunities may be time-sensitive, and users need to act swiftly before market conditions change.

  • Risk of Gas Costs for Arbitrage: Users need to be cautious about gas costs, especially in scenarios where the price difference for arbitrage is minimal, as it may not cover the transaction fees.

-  Why our experts picked it

Furucombo supports a wide array of DeFi strategies, including arbitrage trades, collateral swaps, self-hedging, and more, providing users with options for a range of crypto flash loan use cases.


Best crypto flash loan for arbitrage

For traders well-versed in the intricacies of decentralized finance (DeFi), Uniswap Flash Swaps emerges as a powerful tool offering uncollateralized loans tailored for arbitrage trading. Operating through automated smart contracts, this platform demands technical expertise, making it an optimal choice for seasoned traders seeking advanced DeFi functionalities.

-  Pros & Cons


  • Uncollateralized Loans: Uniswap Flash Swaps facilitates uncollateralized loans, allowing traders to explore arbitrage opportunities without the need for upfront capital.

  • Streamlined Borrowing: The platform leverages automated smart contracts, streamlining the borrowing process and enhancing efficiency for experienced traders.

  • Ideal for Seasoned Traders: Tailored for experienced traders and arbitrageurs, Uniswap Flash Swaps caters to those with a deep understanding of DeFi complexities.


  • Increased Risks for Lenders: The absence of collateral in transactions amplifies risks for lenders, requiring a cautious approach in lending on the platform.

  • Technical Expertise Required: Effectively utilizing Uniswap Flash Swaps demands technical knowledge and experience, making it less suitable for beginners.

  • Not Recommended for Novices: The platform's complexity and associated risks make it unsuitable for beginners in the DeFi space.

-  Why our experts picked it

Uniswap Flash Swaps operates similarly to Aave flash loans, enabling investors to seize arbitrage opportunities without needing upfront capital. With its uncollateralized loans and automated smart contracts, the platform caters to the specific needs of seasoned traders navigating the dynamic landscape of DeFi.

Benefits of flash loans

Here are two of the key benefits of crypto flash loans.

Seizing market opportunities
Flash loans empower users to swiftly capitalize on decentralized finance (DeFi) opportunities. Unlike traditional slow and costly methods, flash loans enable users to act quickly and seize real-time opportunities across various cryptocurrency markets. Traders can respond promptly to short-lived changes, enhancing competitiveness in the dynamic crypto environment.

Swift, complex actions
Flash loans operate at lightning speed, facilitating the rapid execution of complex financial maneuvers. Traditional financial tools often involve multiple steps and transactions, resulting in delays and increased expenses. 

Flash loans streamline processes, allowing users to swap collateral, liquidate assets, and capitalize on price differences in a single transaction. This efficiency saves time and reduces transaction costs, positioning flash loans as a transformative tool in DeFi.

Cons of a crypto flash loan

Crypto flash loans can have drawbacks. Here are a few considerations to consider when looking at such a loan.

Smart contract risks
Flash loans depend on smart contracts, which may contain vulnerabilities that attackers can exploit, leading to unforeseen losses. Regular audits and prompt fixes are essential to maintaining the security of the flash loan ecosystem.

Price changes
Executing large trades with flash loans introduces the risk of price slippage, impacting market prices, especially with substantial capital involved. Traders must carefully assess the potential for price changes to determine the overall viability of engaging in flash loans.

Gas fees
Flash loans often entail higher gas fees, covering the costs of using the blockchain network. Fluctuating gas fees can impact the cost-effectiveness of flash loan transactions, and users need to evaluate whether the fees align with potential profits.

Market risks
The unpredictable nature of cryptocurrency markets introduces inherent risks for flash loan participants. Strategies like arbitrage and liquidations are contingent on specific market conditions, and sudden changes in prices, liquidity, or overall market sentiment can affect the success of these strategies.

Compliance challenges
Engaging in flash loans that exploit market opportunities may expose users to compliance challenges. The evolving legal landscape of decentralized finance requires users to stay informed and adhere to regulations to avoid potential legal complications. Conducting legal checks before utilizing flash loans is essential to navigate compliance issues effectively.

What happens if I can't pay back a flash loan?

Unlike traditional loans that allow for extended repayment periods, a flash loan operates within the confines of a single transaction. If, for any reason, both the lender and borrower fail to adhere to the predetermined rules, the entire loan issuance is prevented. Smart contracts, the backbone of flash loans, ensure that funds do not move unless conditions are met. 

Should the borrower fail to repay the loan within the transaction instantly, the smart contract promptly reverses the transaction, ensuring the money is returned to the lender. This instantaneous and automated process underscores the advantage of using smart contracts.

How to make money with flash loans

Leveraging flash loans for profit requires strategic execution and a true understanding of the crypto market. Primarily, flash loans offer an avenue for substantial gains without risking personal funds. Key strategies for making money with flash loans include:

Arbitrage opportunities
Traders can exploit price discrepancies across various exchanges. By borrowing funds through a flash loan, they can execute rapid buy-low, sell-high trades to pocket the price difference.

Collateral swaps
Flash loans facilitate quick swaps of collateral backing a user's loan for a different type of collateral, optimizing the financial position.

Lower transaction fees
Flash loans consolidate multiple transactions into one, potentially reducing transaction fees. This efficiency is particularly advantageous for those seeking cost-effective trading strategies.

While these strategies offer lucrative possibilities, it's crucial to conduct thorough research on both the lending protocol and the destination of borrowed capital to mitigate risks associated with flash loans.

Taxes on flash loans

Engaging in flash loans within the crypto space introduces unique tax considerations. The decentralized and dynamic nature of these transactions adds complexity to tax obligations. Key points to consider regarding taxes on flash loans include:

Taxable events
Flash loan transactions may trigger taxable events, and it's essential to determine the nature of these events based on regulatory frameworks.

Maintaining detailed records of flash loan transactions, including borrowed amounts, repayments, and associated fees, is crucial for accurate tax reporting.

Professional guidance
Given the evolving nature of crypto taxation, seeking advice from tax professionals well-versed in cryptocurrency transactions can help navigate the complexities and ensure compliance with tax regulations.

Understanding the tax implications of engaging in flash loans is imperative for crypto enthusiasts to avoid potential legal complications and uphold financial transparency.

Schedule a FREE crypto tax consultation

Flash loans FAQs

Here are answers to frequently asked questions about crypto flash loans and how to make money with flash loans.

Are flash loans illegal?

Flash loans, in themselves, are not illegal. However, the ethical and legal usage of flash loans is crucial to avoid potential legal issues.

Can flash loans be used for hacks?

While flash loans themselves are not hacks, improper use or exploiting vulnerabilities in smart contracts during flash loan transactions could lead to security breaches or other malicious activities.

Can I do a flash loan without coding?

Engaging in a crypto flash loan typically involves creating and executing a smart contract. While some platforms offer user-friendly interfaces, a basic understanding of smart contracts and coding concepts benefits customization and advanced strategies.

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Zac McClure
Zac McClureCo-Founder & CEO at TokenTax
Zac co-founded TokenTax after his career in international finance and accounting at JPMorgan, Imprint Capital and Bain. He has worked in more than half-dozen countries and received his MBA from the UPenn Wharton School.
Alex Miles
Reviewed byAlex MilesCo-Founder at TokenTax
Prior to TokenTax, Alex worked as a Product Designer at Dropbox and before that Readmill (acquired by Dropbox). He holds a BS in Digital Information Design - Interactive Media from Winthrop University.

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