Token Standard

Technical specification defining rules, interfaces, and functions that smart contract tokens must implement to ensure interoperability within a blockchain ecosystem, exemplified by ERC-20 (fungible tokens), ERC-721 (NFTs), and ERC-1155 (multi-token), establishing common APIs for transfers, balance queries, approvals, and metadata across wallets, exchanges, and decentralised applications.

Semantic Classification

Content

Definition

A Token Standard is a technical specification that defines the rules, interfaces, and functions that smart contract tokens must implement to ensure interoperability within a blockchain ecosystem. These standards establish common APIs enabling seamless integration across wallets, exchanges, decentralized applications, and other blockchain infrastructure.

Core Standards

ERC-20 (Fungible Tokens)

• Proposed by Fabian Vogelsteller in November 2015

• Defines fungible tokens where each unit is interchangeable

• Required functions: transfer, balanceOf, approve, transferFrom, allowance, totalSupply

• Use cases: stablecoins, governance tokens, utility tokens, ICO tokens

  ERC-721 (Non-Fungible Tokens)

• Proposed by William Entriken et al. in January 2018

• Each token has unique tokenId making it non-fungible

• Tracks ownership via ownerOf function

• Enables unique digital collectibles, art, and real-world asset representation

• Supports metadata URI for off-chain attributes

  ERC-1155 (Multi-Token Standard)

• Developed by Enjin to address ERC-721 limitations

• Supports both fungible and non-fungible tokens in single contract

• Enables batch transfers reducing gas costs and network congestion

• Optimal for gaming assets and mixed token portfolios

  Advanced Standards

• ERC-777: Enhanced security with hooks for token operations

• ERC-998: Composable tokens enabling ownership hierarchies

• ERC-4626: Standardized yield-bearing vault interface for DeFi

• ERC-1400: Security token standard with transfer restrictions

  Technical Characteristics

• Interface Compliance: Contracts must implement required function signatures

• Event Emission: Standards define events for off-chain indexing

• Approval Mechanisms: Two-step transfer patterns for delegated spending

• Metadata Standards: Structured JSON schemas for token attributes

  Cross-Chain Standards

• BEP-20: Binance Smart Chain equivalent of ERC-20

• SPL Tokens: Solana Program Library token standard

• CW-20/CW-721: CosmWasm token standards for Cosmos ecosystem

• TRC-20: TRON network token standard

  Relationships

  Security Considerations

• Reentrancy vulnerabilities in transfer functions

• Integer overflow/underflow in older implementations

• Approval race conditions

• Malicious token contract behaviors

Provenance