How Do You Debug a Smart Contract? The Guide to Debugging!

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A person is programming a smart contract on a computer screen.
Table of Contents
A person is programming a smart contract on a computer screen.

Key Takeaways:

  • Understanding the different categories of smart contract errors, including syntax errors, logical errors, and runtime errors will effective debugging
  • Utilizing powerful debugging tools like Hardhat & Truffle, Remix IDE, and EtherScan can greatly simplify the process
  • Setting up your development environment, configuring Truffle, and deploying with Infura will enhance your ability to debug smart contracts

How Do You Debug a Smart Contract?

To debug a smart contract, use proper debugging tools such as truffle debugger or Remix IDE. You should also thoroughly test your code, analyze error messages and logs, and utilize breakpoints to identify specific areas causing problems.

Navigating through the complexities of debugging a smart contract may feel like uncharted territory for many. As an integral part of Ethereum, these contracts require meticulous attention to detail in order to function flawlessly.

This guide aims to streamline the process for you; offering step-by-step instructions, practical tips, and proven strategies to help uncover and resolve issues effectively. Ready for your deep dive into successful smart contract debugging?

Categories of Ethereum Smart Contract Errors

Ethereum Smart Contract Errors fall into four categories: Syntax Error, Logical Error, Runtime Error, and Common Runtime Errors such as Stack Overflow, Stack Underflow, Execution Reverted, Out-of-Gas, Invalid Opcode, JUMP Errors.

Syntax Error

syntax error in the realm of Ethereum smart contract development refers to an issue faced when the code doesn’t comply with the rules and structure of Solidity, the primary language used for creating these contracts.

It’s a common hiccup encountered by developers, especially beginners learning to master programming languages like Solidity or Clarity. These errors can prevent your smart contracts from executing as expected and might even hinder their deployment on Ethereum, making it crucial for accurate debugging.

Detecting syntax errors involves scrutinizing your code line by line to ensure each command adheres to proper grammar and punctuation rules of Solidity while leveraging tools such as Truffle and Infura can further streamline this process.

Logical Error

Logical errors are common in smart contract development and can be the trickiest to identify and fix. These errors occur when there is a flaw or mistake in the code’s logic, causing unexpected behavior or incorrect results.

Unlike syntax errors that prevent code from compiling, logical errors allow the code to run but produce incorrect outcomes.

Identifying logical errors requires careful analysis of the code and its expected behavior. It involves examining how variables are used, conditions are evaluated, and functions interact within the smart contract.

Logical errors often stem from mistakes in conditional statements, loops, or mathematical calculations.

To debug logical errors effectively, developers should rely on tools like Truffle or Remix IDE to step through their code line by line and inspect variable values at different stages of execution.

They can also employ techniques like console.log statements to print out intermediate values for further analysis.

Common Runtime Errors

Runtime errors are common issues that can occur when executing a smart contract on the Ethereum blockchain. These errors can lead to unexpected behavior and transaction failures. Be aware of these common runtime errors and know how to address them. Here are some of the most common runtime errors in smart contracts:

  1. Stack Overflow: This error occurs when the stack, which is used to store temporary variables during contract execution, exceeds its maximum size.
  2. Stack Underflow: The opposite of stack overflow, this error happens when an operation attempts to retrieve data from an empty stack.
  3. Execution Reverted: When a function call or transaction encounters an exception or error condition, it may revert the entire execution state back to its previous state.
  4. Out-of-Gas: Each transaction in Ethereum requires a certain amount of gas to execute. If a transaction runs out of gas before completing, it will fail with an out-of-gas error.
  5. Invalid Opcode: An invalid opcode error occurs when the contract attempts to execute an invalid or non-existent operation code.
  6. JUMP Errors: Jump errors occur when there are problems with jumping between instructions within the contract’s bytecode.

Debugging Smart Contracts

Learn essential debugging tips and explore powerful tools like Hardhat & Truffle, Remix, and EtherScan to solve common smart contract errors. Discover step-by-step instructions for successfully debugging your Ethereum contracts!

Debugging Tips

  1. Use a Solidity linter to catch syntax errors early in the development process.
  2. Start with small, testable smart contracts to isolate and fix issues more efficiently.
  3. Implement extensive unit tests to identify and resolve logical errors in your code.
  4. Utilize logging statements strategically to trace the flow of execution and pinpoint potential bugs.
  5. Make use of debugging tools like Truffle Debugger or Remix IDE for real-time analysis of your smart contract.
  6. Take advantage of EtherScan’s contract debugger feature to step through your contract’s execution line by line.
  7. Leverage stack traces and error messages provided by Ethereum Virtual Machine (EVM) to troubleshoot runtime errors.
  8. Keep an eye on gas usage and optimize your smart contract’s code to avoid out-of-gas errors during deployment or execution.
  9. Experiment with different input parameters and edge cases during testing to uncover potential vulnerabilities or flaws in your code.
  10. Seek assistance from online communities, forums, or experienced developers when encountering challenging debugging scenarios.

Remember, effective debugging requires a systematic approach, attention to detail, and a thorough understanding of the underlying blockchain technology and programming languages used in smart contract development.

Debugging Tools (Hardhat & Truffle, Remix, EtherScan)

There are several powerful debugging tools available for developers working with Ethereum smart contracts. These tools can greatly simplify the process of identifying and resolving issues in your code. Here are some of the top debugging tools you can use:

  • Hardhat & Truffle: Both Hardhat and Truffle are popular development frameworks that provide built-in debugging capabilities. They allow you to run your smart contracts in a local development environment and step through the code to identify any errors or unexpected behavior.
  • Remix: Remix is an open-source web-based IDE that offers a range of features for developing, testing, and debugging smart contracts. It provides a user-friendly interface where you can compile and deploy your contracts, as well as debug them using breakpoints, variable inspection, and transaction tracing.
  • EtherScan: EtherScan is a blockchain explorer that also offers debugging functionality. With EtherScan, you can analyze transactions and smart contract interactions on the Ethereum network. It provides detailed information about gas usage, events, and function calls, helping you trace the execution flow and identify any issues.

Step-by-Step Instructions for Debugging a Smart Contract

Learn how to set up your development environment, configure Truffle, debug smart contracts locally and online, and deploy them with Infura in this comprehensive guide to successfully debugging Ethereum smart contracts.

Master the art of efficient debugging with our step-by-step instructions and enhance the reliability of your smart contract projects.

Setting Up the Development Environment

To successfully debug a smart contract, set up the development environment properly. Follow these steps to ensure a smooth debugging process:

  1. Install Node.js: Before setting up the development environment, make sure you have Node.js installed on your machine. It will provide the necessary tools and libraries for smart contract development.
  2. Install Truffle Framework: Truffle is a popular development framework that simplifies the process of creating, testing, and deploying smart contracts.
  3. Configure Truffle Project: Create a new directory for your project and navigate to it in the terminal. Initialize a new Truffle project.
  4. Choose a Text Editor: Select a text editor that suits your preferences and supports Solidity syntax highlighting. Some popular choices include Visual Studio Code, Sublime Text, and Atom.
  5. Create Contracts: Within your Truffle project directory, navigate to the `contracts` folder and create your Solidity smart contract files with `.sol` extension.
  6. Write Tests: In the `test` folder of your project, create JavaScript test files with `.js` extension to write unit tests for your smart contracts.
  7. Configure Network Settings: Open the `truffle-config.js` file (or `truffle.js` for older versions of Truffle) in your project root directory and configure network settings such as gas price, network ID, and provider URL.

Configuring Truffle

To successfully debug and deploy smart contracts, configure Truffle, a popular development framework. Follow these steps to get started with Truffle configuration:

  1. Open the command line interface and run the following command: `npm install -g truffle`
  2. Choose a suitable location on your computer and create a new folder for your project.
  3. Navigate to your project directory in the command line and run this command: `truffle init`
  4. Open the truffle – config.js file in a text editor.
  5. Ensure that the network configurations match your desired network settings (e.g., development, testnet, mainnet).
  6. Modify any other desired configurations such as gas limits or contract compilation options.
  7. Uncomment and update the `development` network section with your preferred Ethereum client’s provider URL.
  8. If you want to deploy your smart contracts using Infura, sign up for an account on
  9. Obtain an API key from Infura and update the `infura` section of the truffle – config.js file with your project ID.
  10. If you plan to deploy on multiple networks, add more network sections within the module.exports object in truffle-config.js.
  11. Save all modifications made to the truffle – config.js file before proceeding further.

Debugging Smart Contracts Locally

To successfully debug smart contracts locally, follow these step-by-step instructions:

  1. Set up the development environment: Install Node.js and npm to set up the necessary dependencies for smart contract development.
  2. Configure Truffle: Use Truffle, a popular development framework, to compile and deploy smart contracts locally. Configure Truffle by creating a project directory and initializing it with the desired network settings.
  3. Debug smart contracts: Use debugging techniques such as console.log() statements or using the Solidity debugger to identify errors in your code. By strategically placing these statements in your code, you can track variables’ values and execution flow during runtime.
  4. Analyze transaction inputs: Examine the inputs provided for each transaction executed by the smart contract and verify if they are correct.
  5. Simulate transactions: Utilize a tool like Ganache or Hardhat to simulate transactions locally, enabling you to test and debug your smart contracts without deploying them on the actual network.
  6. Monitor events: Emit events within your smart contracts and use them to track specific actions during execution. Check that the events are emitted correctly according to your expectations.
  7. Test edge cases: Try executing your smart contract with different scenarios, including extreme values for input parameters, to ensure its robustness against potential issues.
  8. Use debugging tools: Take advantage of powerful debugging tools like Remix IDE or Visual Studio Code plugins specifically designed for Ethereum development. These provide additional insights into contract execution by visualizing memory storage, offering breakpoints, and stepping through code line by line.

Deploying Smart Contracts with Infura

To deploy smart contracts with Infura, follow these steps:

  1. Set up an Infura account: Create an account on the Infura website and obtain your unique project ID.
  2. Import your project ID: In your development environment, import the Infura project ID into your configuration file or script.
  3. Install necessary dependencies: Ensure that you have the required libraries and dependencies installed for interacting with Ethereum networks using Infura.
  4. Configure accounts and keys: Add your Ethereum account address and private key to ensure you have access to deploy smart contracts.
  5. Compile your smart contract: Use a Solidity compiler like solc or Truffle to compile your smart contract source code into bytecode.
  6. Write deployment scripts: Create deployment scripts with Truffle, Hardhat, or any compatible tool of your choice. These scripts specify the network configuration and provide instructions for deploying the compiled bytecode onto the network using Infura as the provider.
  7. Specify network settings: Define the network settings in your deployment script, including the network name (e.g., mainnet, rinkeby) and the Infura endpoint URL corresponding to that network.
  8. Deploy your smart contract: Execute the deployment script to initiate the deployment process. This will send a transaction to deploy your smart contract’s bytecode onto the specified Ethereum network through Infura.
  9. Monitor deployment status: Track the progress of your contract deployment by monitoring transaction confirmations on blockchain explorers like Etherscan or by using command-line tools provided by Truffle or Hardhat.
  10. Interact with deployed contract: Once deployed successfully, you can interact with your smart contract by sending transactions or querying its state using its address on the respective Ethereum network.

Debugging Online Smart Contracts

To successfully debug online smart contracts, follow these steps:

  1. Use a reliable debugging tool: Utilize tools like Hardhat & Truffle, Remix, or EtherScan to debug your online smart contracts effectively.
  2. Connect to the network: Make sure you are connected to the appropriate Ethereum network where your smart contract is deployed. This will enable you to interact with the contract and debug its functionality.
  3. Access contract details: Retrieve the block number and transaction hash associated with your online smart contract. This information will help you analyze and troubleshoot any issues that may arise during debugging.
  4. Analyze transaction failure: If your smart contract encounters a transaction failure, use the provided block number and transaction hash to investigate the cause of the error. This could be due to various factors such as gas limit constraints, invalid opcodes, or other runtime errors.
  5. Use a visual debugger: Consider using a visual debugger like Tenderly Debugger for a more efficient debugging process. These tools provide advanced features such as memory/storage visualization and step-by-step analysis of each transaction’s execution.
  6. Follow troubleshooting techniques: Employ proven methods for identifying and resolving common smart contract errors. Debugging techniques such as analyzing logs, event emissions, and input/output data can help pinpoint potential issues within your online smart contract.

Best Practices for Testing and Deployment

Discover the essential prerequisites, Solidity best practices, and proven debugging strategies to ensure the reliability and success of your smart contract deployment. Master the art of testing, troubleshooting, and enhancing smart contracts for optimal performance.


Before diving into the process of debugging smart contracts, there are a few prerequisites that you need to keep in mind. Here are the key things you should have in place before getting started:

  1. Solidity Knowledge: Familiarize yourself with the Solidity programming language, which is used for writing smart contracts on Ethereum. It is essential to understand Solidity’s syntax, data types, control structures, and function declarations.
  2. Development Environment Setup: Set up a development environment that allows you to write and test your smart contracts effectively. This typically involves installing necessary tools such as Node.js, npm (Node Package Manager), and a code editor like Visual Studio Code.
  3. Truffle Framework Installation: Install the Truffle framework, which provides an extensive suite of development tools for Ethereum smart contract development. Truffle simplifies tasks like compiling contracts, managing migrations, and running tests.
  4. Ganache or Local Ethereum Network: Set up a local blockchain network using either Ganache or another Ethereum client. This allows you to deploy and test your smart contracts locally without incurring any gas fees.
  5. Ether Balance and Gas: Make sure you have a sufficient balance of Ether in your account to cover gas costs associated with deploying transactions and executing functions within your smart contracts.


Solidity is a programming language specifically designed for writing smart contracts on the Ethereum blockchain. It is widely used by developers to create decentralized applications (DApps) and execute self-executing contracts.

Solidity allows developers to define the rules and logic of their smart contracts, specifying how they should operate and interact with other smart contracts or users.

By using Solidity, developers can write code that is both secure and transparent, ensuring the integrity of their smart contract applications. Solidity supports various features like inheritance, events, modifiers, and libraries that make it flexible for creating complex applications on Ethereum.

It provides built-in data types such as integers, booleans, addresses, strings, arrays, and structs.

Understanding Solidity is key for debugging smart contracts effectively. By mastering this programming language and its syntax intricacies, developers can identify potential errors or logical issues in their code more efficiently.

Testing and Debugging Strategies

Testing and debugging are crucial aspects of smart contract development. To ensure the reliability and security of your smart contracts, employ effective testing and debugging strategies. Here are some proven methods to consider:

  1. Conduct Unit Testing: Break down your smart contract code into smaller components and test each component individually. This helps identify any errors or bugs in specific parts of your code.
  2. Write Comprehensive Test Cases: Develop a set of comprehensive test cases that cover various scenarios and edge cases. This will help you uncover any unexpected behavior or vulnerabilities in your smart contract.
  3. Use Emulators and Simulators: Utilize emulators or simulators to replicate real-world conditions and test the performance of your smart contracts under different network conditions. This can help you identify potential issues related to scalability, gas consumption, or transaction confirmation times.
  4. Implement Automated Testing: Automate the testing process by using frameworks like Truffle or Hardhat to run tests automatically whenever changes are made to the codebase. This ensures consistent and thorough testing throughout the development process.
  5. Perform Integration Testing: Test the interaction between your smart contract and other external contracts or systems on which it relies. This will help identify any compatibility issues or conflicts with external dependencies.
  6. Security Audits: Consider conducting security audits by hiring third-party experts who specialize in reviewing smart contracts for vulnerabilities such as reentrancy attacks, input validation issues, or improper access control.
  7. Debugging Tools: Take advantage of debugging tools like Remix IDE, Visual Studio Code with Solidity extensions, or Tenderly debugger. These tools provide features such as executing step-by-step debugging, variable inspection, stack visualization, and transaction trace analysis.
  8. Peer Reviews: Engage with other experienced developers in the blockchain community for peer reviews of your codebase. Fresh perspectives can often uncover errors or suggest improvements that you may have missed.


What Are the Types of Errors That Can Occur in a Smart Contract?

There are several types of errors that can occur in a smart contract. Some common errors include runtime errors, logic errors, gas errors, syntax errors, and security vulnerabilities.

How Can a Debugger Help in Debugging Solidity Smart Contracts?

A debugger provides advanced tools for debugging solidity smart contracts. It allows you to set breakpoints, step through the code line by line, inspect variables and function calls, and track the gas used during execution.

Can I Debug a Transaction That Doesn’t Revert or Throw an Error?

Yes, you can still debug a transaction even if it doesn’t revert or throw an error. The debugger allows you to track the state changes and analyze the execution flow, which can be helpful in identifying and fixing any issues or unexpected behavior.

What Should I Do if I Encounter a Stack Overflow or Stack Underflow Error?

If you encounter a stack overflow or stack underflow error, you should review your smart contract code for any recursive function calls or incorrect usage of stack operations. Adjusting the code logic or data structures can help prevent these errors.

How Can I Start Debugging a Smart Contract?

To start debugging a smart contract, you need to deploy it to a test network or a local development environment. Then, you can connect the debugger to the deployed contract and set breakpoints to examine the execution flow.

What Are Some Common Debugging Techniques for Smart Contracts?

Some common debugging techniques for smart contracts include using console.log statements to print values, reviewing the contract’s business logic, examining the gas used during execution, and analyzing the function calls and variable assignments.

Can a Debugger Help in Identifying Errors in the Solidity Code?

Yes, a debugger can help identify errors in the solidity code. It allows you to step through the code, inspect variable values, and track the execution flow, which can help pinpoint any problematic lines of code.

Is It Possible to Debug a Function That Doesn’t Exist in My Smart Contract?

No, you cannot debug a function that doesn’t exist in your smart contract. The debugger can only debug the existing functions and their execution flow. If you are encountering issues with a non-existing function, you should review your contract’s code and make sure the function is defined correctly.

What Should I Do if I Encounter a Gas Error During Contract Execution?

If you encounter a gas error during contract execution, you should review your code for any gas-intensive operations or unnecessary gas consumption. Optimizing your code and avoiding gas-guzzling operations can help mitigate gas errors.

Conclusion: How to Debug Ethereum Smart Contracts

Successfully debugging a smart contract is key for ensuring its reliability and functionality on the Ethereum blockchain. By following step-by-step instructions and utilizing debugging tools such as Truffle and Infura, developers can effectively identify and resolve common errors like syntax errors, logical errors, and runtime errors.

Testing and deploying smart contracts with caution, using best practices and solid programming languages like Solidity or Clarity, will also contribute to enhancing their overall quality. Remember that understanding blockchain fundamentals is essential in this process.

By mastering smart contract debugging techniques, developers can create robust decentralized applications that meet the needs of users while promoting trust in the blockchain ecosystem.



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About the Author:
Alex Sterling stands at the forefront of blockchain innovation, offering a technical perspective rooted in a Computer Science background. Specializing in decentralized systems, Alex's articles dissect blockchain technologies and crypto market trends, making intricate details comprehensible for readers. They are deeply involved in blockchain project development, frequently sharing their technical expertise at tech conferences. Alex's work aims to educate and inspire readers about the transformative potential of blockchain and cryptocurrency.