The Ultimate Guide to ERC-20 Tokens: What You Need to Know

Andrew Carr
| Editor:
March 8, 2024
5 min read

Introduction: What is a token standard?

Token standards in cryptocurrency are pivotal frameworks governing digital tokens' creation, functionality, and interaction within blockchain ecosystems. These standards establish a set of predefined protocols that ensure consistency, interoperability, and compatibility across various tokens and decentralized applications (DApps).  

Among the most renowned standards is the Ethereum ERC-20 token standard. These standards typically encompass token issuance, transfer, and ownership rule sets.

Why are token standards necessary? 

Cryptocurrency token standards enable interoperability so that native coins of one blockchain can be transferred to and traded on another. This interoperability facilitates token exchange and transfer across different platforms and services, fostering the development of intricate decentralized systems. 

Additionally, this ensures that tokens adhering to the same standard can integrate seamlessly with wallets, exchanges, and third-party tools supporting the designated protocol. This compatibility enhances user experiences by providing uniform interfaces and functionalities across various applications and platforms, simplifying token management and utilization for developers and users. 

By adhering to well-defined standards, developers can leverage established best practices and security mechanisms to mitigate risks and vulnerabilities, safeguarding the integrity and resilience of tokenized assets.

Flexibility and Community Adoption

Flexibility in token standards allows developers to customize tokens to meet specific use cases and requirements. Through features such as token minting, burning, pausing, freezing, and metadata management, developers can implement innovative token models that cater to diverse business needs and user preferences.  

Community adoption plays a crucial role in the success and proliferation of token standards, as widespread acceptance and endorsement foster collaboration, innovation, and growth within the ecosystem.  

In essence, token standards serve as foundational frameworks for creating and managing digital tokens on blockchain platforms. By promoting interoperability, flexibility, and community adoption, token standards enable the seamless integration and evolution of DApps, driving the innovation and adoption of blockchain technology.

How ERC-20 Came to Be

In the early days of Ethereum, developers faced challenges in standardizing token creation and interaction, leading to fragmentation and inefficiencies within the network. Without standard rules and protocols governing token behavior, interoperability between different tokens and applications posed significant hurdles for developers and users. 

Recognizing the need for a unified token standard, Fabian Vogelsteller, a developer in the Ethereum community, proposed the ERC-20 standard in late 2015. ERC-20 stands for "Ethereum Request for Comments 20," following the Ethereum Improvement Proposal (EIP) process for proposing changes and enhancements to the Ethereum protocol.

The ERC-20 proposal outlined a set of six mandatory functions and two optional functions that define the essential utility of Ethereum tokens. The mandatory functions include:

  • totalSupply: This function returns the total supply of tokens issued by the contract.
  • balanceOf: Used to query the balance of tokens for a specified address.
  • transfer: Facilitates the transfer of tokens from the caller's address to another address (a caller is a user requesting a transaction).
  • transferFrom: Allows authorized addresses to transfer tokens on behalf of the token owner.
  • approve: Permits the token owner to authorize another address to spend a specified number of tokens.
  • allowance: Enables querying the amount of tokens approved for spending by one address on behalf of another.

 The optional functions are as follows:

  • name: An optional function that returns the name of the token.
  • symbol: A function that provides the symbol or ticker representing the token.

These functions facilitate token transfers between Ethereum addresses, balance inquiries, and approval mechanisms for delegated token transfers. 

Developers quickly adopted ERC-20 as the de facto standard for token issuance, paving the way for the explosive growth of initial coin offerings (ICOs), decentralized finance (DeFi) protocols, and other token-based projects on the Ethereum blockchain. 

One of the key drivers behind ERC-20's widespread adoption was its simplicity and versatility. The standard's straightforward implementation allowed developers to create and deploy tokens relatively quickly, while its flexibility accommodated a wide range of use cases and functionalities. ERC-20 tokens could represent anything from utility tokens powering DApps to asset-backed tokens representing physical or digital assets.

The Role of ERC-20 in Ethereum

Today, the ERC-20 token standard outlines rules and functions for creating and managing fungible tokens that can be exchanged for equal value and replicated within the Ethereum network.  

ERC-20 tokens leverage Ethereum's smart contract functionality, deploying token contracts encapsulating the standard's required functionalities. Each ERC-20 token contract maintains a ledger of token balances associated with Ethereum addresses, which users can manipulate through the standardized functions defined by ERC-20.  

This architecture ensures that ERC-20 tokens exhibit consistent behavior and interact seamlessly with other Ethereum-based applications and services. 

Furthermore, the ERC-20 standard allows for creating tokens with customizable attributes, including total supply, token name, symbol, and decimal precision, providing flexibility for developers to tailor tokens to specific operational needs.

ERC-20 Functions Explored 

Transfer Function

Of the mandatory and optional functions that the ERC-20 proposal outlined, the “transfer” function is the most foundational. This function is embedded in Ethereum smart contracts to enable direct token transfers from a sender's address to a specified Ethereum address. 

Its signature typically includes two parameters: “to,” which denotes the recipient's Ethereum address, and “value,” representing the number of tokens to be transferred.

Before initiating the transfer process, the function undergoes a series of validations that ensure the sender possesses a sufficient token balance to cover the transfer amount. These validations also verify the validity of the recipient's address while safeguarding against potential overflow or underflow conditions to prevent unintended consequences.  

Overflow occurs when the result of adding tokens to a balance exceeds the maximum value that the data type used to store the balance can represent. Similarly, underflow happens when subtracting tokens results in a value below the minimum representable value for the data type. Both conditions can lead to the corruption of data.  

Upon successful validation, the smart contract deducts the designated token amount from the sender's balance and updates the recipient's balance correspondingly. This seamless transaction mechanism ensures atomicity and preserves balance consistency across Ethereum addresses. Atomicity in blockchain refers to all components of a transaction executing and completing as a whole; either the transaction goes through or doesn’t, and no component is completed in part. 

Post-execution, the smart contract emits a “Transfer” event, enhancing transparency by furnishing details such as the sender's address, the recipient's address, and the transferred token quantity. This event empowers external observers to track token movements on the blockchain effectively. 

Finally, the transfer function returns a boolean value—a data point representing truth or falsehood to denote the outcome of a logical condition—signifying the success or failure of the transfer operation. This returned boolean value allows callers to manage transfer outcomes, programmatically responding appropriately to transaction results.

BalanceOf Function

Another essential function outlined by the original ERC-20 proposal is the “balanceOf” function, which enables users and DApps to query the balance of tokens associated with a specific Ethereum address.  

The “balanceOf” function only requires one parameter: “owner.” The “owner” parameter specifies the Ethereum address for which the token balance is queried. When invoked, the “balanceOf” function retrieves the token balance associated with the specified Ethereum address. This balance represents the number of tokens the address holds within the ERC-20 token contract. 

The “balanceOf” function finds extensive utility across DApps and token-based protocols. For example, wallets and portfolio trackers utilize the “balanceOf” function to give users insights into their token holdings and overall account balances.  

DEXs rely on the “balanceOf” function to verify token ownership and facilitate swaps and trades effectively. Moreover, smart contracts leverage the “balanceOf” function to enforce token-based functionalities like staking, voting, or reward distribution based on users' token balances. 

Given its role in transparency, accountability, and usability within the ERC-20 token ecosystem, the “balanceOf” function is indispensable. It grants users real-time visibility into token ownership, enabling informed decisions regarding token transfers, transactions, and interactions on the Ethereum blockchain.

The Impact of ERC-20

ERC-20, the most widely adopted token standard on the Ethereum blockchain, has profoundly influenced the development of other token standards and protocols within the cryptocurrency ecosystem.  

ERC-20 set a precedent for interoperability and compatibility among tokens and DApps. Other token standards, such as ERC-721 (Non-Fungible Tokens) and ERC-1155 (Multi-Token Standard), have ensured compatibility with ERC-20 tokens, allowing seamless interaction and integration within the Ethereum ecosystem. ERC-721 allows the creation of NFTs, and ERC-1155 enables the creation of fungible and non-fungible tokens within the same contract. 

The principles and concepts underlying ERC-20 have transcended Ethereum, inspiring the development of token standards on other blockchain platforms such as BEP-20 on the Binance Smart Chain, TRC-20 on Tron, and SPL on Solana. All of which facilitates token creation and interoperability in multi-chain environments.


In conclusion, the ERC-20 token standard has profoundly impacted the cryptocurrency ecosystem, particularly within the Ethereum blockchain. ERC-20 has enabled interoperability, compatibility, and innovation across DApps and tokenized economies by providing a standardized token creation, transfer, and management framework.  

Standardizing token functionality has simplified token management for developers and users alike, promoting transparency, security, and reliability within Web3. 

Furthermore, ERC-20's success has inspired the development of other token standards, such as ERC-721 for NFTs on Ethereum and ERC-1155 for multi-token standards, expanding the possibilities for digital asset creation and interaction. 

Beyond Ethereum, the principles of ERC-20 have transcended to other blockchain platforms, fostering interoperability and collaboration across multiple blockchain networks.

Overall, ERC-20's legacy continues to shape the trajectory of tokenization and DeFi, driving the adoption and evolution of blockchain technology. As the cryptocurrency landscape continues to evolve, ERC-20 remains a cornerstone of token standards, paving the way for further innovation and integration within decentralized systems and digital asset markets.

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