Internal transactions are a fundamental aspect of blockchain, playing a crucial role in executing smart contracts and facilitating various interactions within decentralized systems. Understanding internal transactions is essential for understanding the inner workings of blockchain.

In this guide, we'll look into internal transactions, discussing their significance in smart contract execution and their broader impact on blockchain applications. Our goal is to simplify their fundamentals to make them understandable for both newbies and experienced blockchain developers.

Understanding Internal Transactions

In Ethereum, there are two primary types of addresses: external addresses (EOA) and internal (Contract) addresses. External addresses, typically associated with user wallets, are used for sending and receiving tokens (fungible or non-fungible) and interacting with smart contracts. On the other hand, contract addresses are unique in that they are associated with deployed smart contracts rather than individual users. These addresses serve as the location where the smart contract code is stored and executed on the blockchain.

Smart contracts are self-executing agreements with the terms of the contract directly written into code. Stored at contract addresses, these contracts are capable of performing a variety of functions autonomously when triggered by predefined conditions. This leads us to the concept of internal transactions, which are key to understanding how Ethereum functions beyond simple transfers of tokens.

Internal transactions refer to the transfer of value or data between accounts or contracts within the Ethereum chain. Unlike external transactions, which involve transfers of assets between distinct external addresses, internal transactions occur entirely within the blockchain's ecosystem. These transactions are primarily facilitated through the execution of smart contracts. When a smart contract at a contract address is activated, it can autonomously execute actions, including transferring funds or calling functions of other contracts, leading to  internal transactions.

Types of Internal Transactions

Token Transfers Initiated by Smart Contracts

One of the most common types of internal transactions involves the transfer of tokens between addresses triggered by smart contract functions. These transactions can represent various actions, such as token swaps, or token distribution within decentralized applications (dApps).

Interactions Between Different Smart Contracts

Internal transactions also occur when smart contracts interact with each other, such as calling a function from another smart contract.

Mechanics Behind Internal Transactions

Internal transactions on the Ethereum blockchain are typically initiated in two ways: either through user interactions with decentralized applications (DApps) or by external events that trigger functions within a smart contract. When a user interacts with a DApp, for instance by executing a function that requires a transaction, this request is broadcasted to the entire network.

The process begins when the transaction is picked up by validators. In the context of Ethereum, validators play a crucial role in the network's proof-of-stake consensus mechanism.If the transaction involves a smart contract, the next step is the execution of the contract's code. This execution can lead to one or more internal transactions depending on the logic defined in the contract. The execution process could includes:

  • Input Validation: The smart contract checks that all inputs meet the predefined criteria to ensure they are valid. 

  • State Changes: If the inputs are valid, the contract proceeds to modify its internal state. This could involve updating stored values, such as account balances or ownership records.

  • Triggering of Events: During or after the state changes, the smart contract may emit events. These events are signals that an action  has occurred within the contract, such as a transfer of tokens or a change in ownership. 


Smart Contract Events Tracking

  • Detailed Information about Contract Interactions: Offers insights into users' engagements with smart contracts on the blockchain, displaying information such as parameters passed, resulting state changes, and transaction details associated with each interaction.

  • Detailed Information about Token Transfers: Enables users to track the movement of tokens within the blockchain network, including sender and recipient addresses, transfer amounts, transaction timestamps, and hashes, facilitating transparency and verification of token transfers.

Batch Transaction Verification

Internal transactions provide a convenient way to verify the completion of batch transactions by monitoring the internal state changes within the blockchain network. Users can track the progress of batch transactions and confirm the action triggered from the smart contract was successful.

Tools for Tracking Internal Transactions

  • Etherscan: Etherscan provides users with a comprehensive platform to explore and analyze blockchain data, including internal transactions. Users can search for specific transactions, view transaction details, and track internal transactions within smart contracts. Etherscan offers valuable insights into the activity and state changes occurring within the Ethereum ecosystem.

  • Tatum: With the Tatum SDK, developers can integrate blockchain functionality into their applications, and also monitor internal transactions.

  • Tenderly: Tenderly is a blockchain monitoring and debugging platform designed for Ethereum developers. It offers features for tracking smart contract interactions, including internal transactions, and provides real-time insights into contract execution and state changes. 


Having explored what internal transactions are, from understanding their basics to how they work, it's clear that they play a crucial role in the functionality of blockchain. This deep dive into their mechanism should provide users and developers alike with a better understanding of how these transactions enhance the efficiency and transparency of decentralized systems.