What is a Smart Contract?

Smart Contracts are essential to many blockchain applications. This page covers everything you need to know as an entry to smart contracts.

Smart contracts function similarly to traditional contracts by defining the terms of an agreement. However, unlike traditional contracts, smart contract conditions are executed as code on a blockchain like Ethereum. This technological innovation enables developers to build applications that leverage blockchain's security, reliability, and accessibility while offering cutting-edge peer-to-peer functionality. This includes diverse applications ranging from financial instruments, logistics, to gaming.

Key Characteristics

  • Autonomy: Smart contracts operate independently once deployed on the blockchain.

  • Transparency & Verifiability: The contract's code is public, allowing for transparency and trust.

  • Immutability: Once a smart contract is deployed, it typically cannot be altered.

Importance of Smart Contracts

Smart contracts are foundational in developing a wide range of decentralized applications (dApps) and tokens. They are integral to sectors like finance, logistics, and gaming, providing a framework for complex financial transactions, peer-to-peer exchanges, and more. All transactions executed through smart contracts are stored on the blockchain, ensuring security and transparency.

  • Uniswap: A decentralized exchange using smart contracts for trading crypto without a central authority controlling exchange rates.

  • Compound: Enables earning interest and borrowing instantly through smart contracts, bypassing traditional banking services.

  • USDC: A cryptocurrency pegged to the US Dollar via smart contracts, representing a new category of digital money known as Stablecoins.

How Smart Contracts Work

On Ethereum and Other Blockchains

While Ethereum is the most popular platform for smart contracts, they can also run on other blockchains like EOS, Neo, Tezos, and more.

Development and Deployment

  • Languages: Smart contracts are written in languages like Solidity, Web Assembly, and Michelson.

  • Ethereum Network Storage: On Ethereum, contract code is stored on the blockchain and can be reviewed by anyone for transparency and functionality.

  • Execution Across Nodes: When a smart contract receives funds, its code is executed by all nodes in the network to reach a consensus on the outcome, facilitating secure execution without centralized oversight.

Gas Fees and Execution

  • To execute a smart contract on Ethereum, a "Gas Fee" is usually required. This fee keeps the blockchain operational.

  • Immutability Post-Deployment: Typically, once running on the blockchain, smart contracts cannot be modified, even by their creator, ensuring resistance to censorship or shutdown.

Practical Scenarios

Imagine you want to convert Ethereum to USDC. You could deposit Ethereum into Uniswap, which would use a smart contract to automatically find the best exchange rate and execute the transaction. Similarly, you could lend your USDC in Compound, earning an algorithmically determined interest rate, all without involving traditional financial institutions.

Advantages Over Traditional Finance

  • Currency Exchange: More efficient and cost-effective compared to traditional finance.

  • P2P Lending: Enables lending your assets as loans globally, which is not as straightforward in conventional settings.


Smart contracts represent a paradigm shift in how we approach agreements and transactions in the digital age. As a developer, it's exciting to be at the forefront of this revolution, crafting contracts that not only automate processes but also open up new avenues for decentralized applications and financial systems. The potential of smart contracts is vast, and we're just scratching the surface of what can be achieved with this transformative technology.

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