Token metadata is the descriptive information attached to a blockchain token that defines its identity, properties, and visual representation. It is the data that answers what the token is, separate from its on-chain ledger entry which only records who owns it and how many exist. This information is typically stored off-chain (e.g., in a decentralized file system like IPFS or a centralized server) and is referenced by a URI (Uniform Resource Identifier) stored within the token's smart contract. Common metadata standards include the Ethereum ERC-721 and ERC-1155 schemas for NFTs, and the SPL Token standard for Solana.
LABS
Glossary
Token Metadata
Token metadata is the descriptive data attached to a blockchain token, defining its properties like name, symbol, and visual representation, often referenced via a URI.
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definition
BLOCKCHAIN GLOSSARY
What is Token Metadata?
Token metadata is the structured data that defines the properties, attributes, and off-chain information of a digital asset on a blockchain.
A standard metadata schema includes several core fields. The name and symbol provide the token's human-readable identifier and ticker. The description offers a detailed explanation of the asset. The image or animation_url points to the visual or multimedia content representing the token. Crucially, attributes or properties are key-value pairs that define unique characteristics, such as rarity traits for an NFT (e.g., Background: Space, Rarity: Legendary). This structured data enables wallets, marketplaces, and explorers to display the token correctly to users.
The storage and integrity of metadata are critical for long-term persistence and value. Because storing large files directly on-chain is prohibitively expensive, the common pattern is to store the metadata JSON file and its associated media on decentralized storage like IPFS (InterPlanetary File System) or Arweave. The on-chain token then holds a hash (like a CID for IPFS) of this data, creating a cryptographically verifiable link. This ensures the metadata is immutable and tamper-proof; if the off-chain file changes, the hash will not match, signaling a potential issue. Centralized HTTP URLs are also used but introduce a single point of failure and trust.
For developers, interacting with token metadata involves querying the token's smart contract for the metadata URI and then fetching and parsing the JSON data from that location. Libraries and indexers simplify this process. The evolution of metadata standards continues with extensions like ERC-4906 (NFT Metadata Update Notification) and ERC-7496 (NFT Dynamic Traits), which allow for secure and verifiable updates to token attributes, supporting more complex use cases like evolving game items or updatable credentials without compromising the core ownership record on the blockchain.
how-it-works
BLOCKCHAIN GLOSSARY
How Token Metadata Works
An explanation of the data structures and standards that define a token's properties beyond its on-chain balance.
Token metadata is the descriptive information attached to a digital asset that defines its properties, appearance, and behavior beyond its core on-chain identifier and balance. This data, which includes the token's name, symbol, decimals, and for NFTs, its visual artwork or traits, is typically stored off-chain for efficiency and referenced via a URI (Uniform Resource Identifier) recorded in the token's smart contract. Standards like Ethereum's ERC-20 and ERC-721 formalize the structure for this reference, separating the immutable, lightweight contract logic from the potentially mutable, rich metadata.
The most common architectural pattern involves a metadata URI pointing to a JSON file hosted on a decentralized storage network like IPFS (InterPlanetary File System) or Arweave. This JSON file follows a schema defined by the token standard, such as the OpenSea metadata standard for NFTs, which specifies fields for name, description, image, and attributes. By storing the data off-chain, smart contracts avoid the prohibitive gas costs of storing large files directly on the blockchain, while the cryptographic hash (like an IPFS Content Identifier or CID) in the URI ensures the data's integrity and permanence.
Dynamic NFTs illustrate a more advanced use of metadata, where the linked JSON file or its attributes can change based on external conditions or on-chain events. This is achieved through oracles that feed data to the smart contract, which then updates the token's metadata URI to point to a new file, or via decentralized compute protocols that generate the metadata response on-demand. This mechanism enables tokens that evolve, represent real-world assets with fluctuating states, or provide programmable utility, moving beyond static digital collectibles.
For fungible tokens (ERC-20), metadata is usually simpler and often embedded directly in the contract via view functions like name() and symbol(), though it can also be referenced off-chain for richer data like detailed project information. The reliability of token metadata hinges on the chosen storage solution; IPFS offers content-addressed permanence if pinned, while traditional web URLs (http://) create a central point of failure. As such, the choice of metadata storage is a critical decision impacting the longevity and decentralization of the tokenized asset.
key-features
TOKEN METADATA
Key Features
Token metadata is the structured data that defines a token's properties, appearance, and behavior, extending its utility beyond a simple balance.
01
On-Chain vs. Off-Chain Storage
Metadata can be stored on-chain (immutable, expensive) or off-chain (flexible, cheap). The token URI in a smart contract points to this data, which is often hosted on decentralized storage like IPFS or Arweave to ensure persistence and censorship-resistance.
02
Standardized Schemas (ERC-721 & ERC-1155)
Interoperability is achieved through standardized metadata schemas. ERC-721 and ERC-1155 tokens use a JSON structure defining:
nameanddescriptionimageoranimation_urlattributesfor traits (e.g.,{"trait_type": "Rarity", "value": "Legendary"}) This allows wallets and marketplaces to display tokens uniformly.
03
Dynamic & Evolving Metadata
Unlike static NFTs, dynamic NFTs have metadata that changes based on external conditions or on-chain events. This is enabled by a smart contract that updates the token URI. Use cases include:
- Gaming items that level up
- Identity credentials that expire
- Art that changes with the weather or price feeds
04
The Role of Token Standards
Standards like ERC-20, ERC-721, and ERC-1155 specify minimal metadata interfaces (name, symbol, decimals). Extended metadata standards, such as ERC-4906 (Metadata Update Notification) and ERC-5192 (Minimal Soulbound NFTs), formalize how changes are signaled and interpreted by applications.
05
Verification & Provenance
Authenticity is critical. Metadata should include cryptographic proofs linking the digital asset to its creator. Best practices involve:
- Hashing the metadata file and storing the hash on-chain.
- Using signed messages from the creator's wallet.
- Referencing immutable, decentralized storage to prevent tampering after minting.
06
Utility Beyond Art: RWA & Identity
Metadata enables tokens to represent complex real-world assets (RWA) and verifiable credentials. Examples include:
- Real Estate: Parcel numbers, legal descriptions, and title documents.
- Supply Chain: Batch numbers, manufacturing dates, and quality certificates.
- Identity: Educational degrees, professional licenses, and KYC status, often using Verifiable Credentials (VCs) standards.
STORAGE LOCATION
On-Chain vs. Off-Chain Metadata
A comparison of the two primary methods for storing token metadata, detailing their core characteristics, trade-offs, and typical use cases.
| Feature | On-Chain Metadata | Off-Chain Metadata |
|---|---|---|
Storage Location | Data is stored directly within the smart contract or transaction data on the blockchain. | Data is stored on external systems (e.g., centralized servers, IPFS, Arweave). |
Data Immutability | ||
Decentralization | ||
Data Accessibility | Guaranteed by blockchain consensus; accessible as long as the chain exists. | Depends on the availability and uptime of the external host. |
Storage Cost | High (paid in gas/transaction fees) | Low to negligible |
Data Size Limit | Severely constrained by block gas limits | Effectively unlimited |
Update Flexibility | Immutable or requires a new transaction | Easily mutable by the controlling party |
Typical Use Case | Critical, immutable attributes (e.g., token supply, royalty config) | Dynamic or rich media (e.g., artwork, descriptions, traits) |
common-standards
TOKEN METADATA
Common Metadata Standards
Token metadata standards define the structure and location of off-chain data—such as name, symbol, and artwork—that describes a token's properties. These standards ensure interoperability across wallets, explorers, and marketplaces.
ecosystem-usage
TOKEN METADATA
Ecosystem Usage & Examples
Token metadata is the descriptive data that defines a token's properties, enabling wallets, explorers, and dApps to display and interact with it correctly. These examples illustrate its critical role across the blockchain stack.
01
Wallet & Explorer Display
Wallets and block explorers use metadata to present a human-readable interface. This includes:
- Token Name & Symbol: Displaying "USD Coin" (USDC) instead of a contract address.
- Decimals: Correctly formatting amounts (e.g., 1,000,000 units shown as 1.0 USDC).
- Logo: Showing the official token icon for easy visual identification. Without accurate metadata, users see only raw, confusing hexadecimal data.
02
DEX & Trading Interface Integration
Decentralized exchanges (DEXs) rely on metadata to build their trading interfaces. Key integrations include:
- Liquidity Pools: Identifying token pairs and calculating exchange rates based on decimals.
- Price Feeds: Associating symbols with off-chain price oracle data.
- Token Lists: Curated lists (like Uniswap's) use metadata to verify and display legitimate assets, protecting users from scams.
03
NFT Marketplaces & Provenance
For Non-Fungible Tokens (NFTs), metadata is essential for representing the digital asset itself. It typically includes:
- Media URI: A link to the image, video, or other content (often stored on IPFS or Arweave).
- Attributes/Properties: Defining rarity, traits, and characteristics for collections.
- Creator Information: Establishing provenance and royalty specifications for secondary sales.
04
DeFi Protocol Logic & Compliance
DeFi protocols use metadata for on-chain logic and regulatory compliance.
- Collateral Valuation: Lending protocols use the token symbol and decimals to query price oracles and determine loan-to-value ratios.
- Compliance Flags: Metadata can signal if a token has transfer restrictions (e.g., for securities compliance).
- Reward Token Identification: Staking and farming contracts identify the correct asset for distributing rewards.
05
Standards: ERC-20, ERC-721, ERC-1155
Token standards define how metadata is structured and accessed.
- ERC-20 (
name,symbol,decimals): The foundational standard for fungible tokens. - ERC-721 (
tokenURI): Returns a URI pointing to a JSON file containing the NFT's metadata. - ERC-1155 (
uri): A multi-token standard where the URI can point to metadata for an entire token class, enabling efficiency for games and collections.
06
Metadata Registries & Extensions
To improve discovery and reliability, ecosystems use metadata registries and extensions.
- Token Lists: Community-maintained JSON files (used by Uniswap, CoinGecko) that bundle address and metadata for verification.
- ERC-1046 & ERC-4824: Proposed standards for on-chain SVG-based logos and common metadata interfaces.
- Chainlink Proof of Reserve: Uses metadata to identify reserve assets, enabling verifiable audits for stablecoins and wrapped assets.
security-considerations
TOKEN METADATA
Security & Reliability Considerations
Token metadata is a critical attack vector and reliability concern. These cards detail the primary risks, attack patterns, and best practices for secure implementation.
02
Spoofing & Phishing Attacks
The lack of a canonical, on-chain registry for token symbols and names enables spoofing attacks. Malicious actors can deploy tokens with identical metadata (name, symbol, decimals) to legitimate ones, tricking users into trading worthless assets.
- Key Vulnerability: The
symbolfield is not unique or verified on-chain. - User Defense: Always verify the token contract address directly from the project's official source, not just the symbol displayed in a wallet.
- Protocol Defense: DEX aggregators and wallets use token lists (like Uniswap's) with strict curation and multi-signature governance to mitigate this risk.
03
Metadata Injection & Malicious Content
The fields within metadata JSON files are not sanitized by protocols. An attacker can inject malicious scripts or misleading data into fields like the description or extensions.
- Cross-Site Scripting (XSS): If a front-end improperly renders metadata as HTML, injected scripts could compromise user wallets.
- Social Engineering: Fake project URLs or handles in the
websiteorsocialfields can lead to phishing sites. - Best Practice: Front-ends must sanitize all user-facing metadata and treat it as untrusted input. Use allowlists for URL schemes and domains.
06
Standardization Gaps & Fragmentation
Multiple, often incompatible metadata standards (ERC-20, ERC-721, ERC-1155, SPL Token) and extension proposals create fragmentation. Wallets and explorers must support numerous schemas, increasing complexity and the attack surface for parsing errors.
- Interoperability Challenge: A wallet may not correctly display a token using a newer metadata extension.
- Validation Difficulty: No universal schema validator exists for on-chain verification.
- Industry Response: Efforts like EIP-5219: Token Metadata Standard aim to create a unified, forward-compatible schema for all token types, improving security through consistency.
TOKEN METADATA
Common Misconceptions
Token metadata is a foundational layer for digital assets, yet its implementation and implications are often misunderstood. This section clarifies the technical realities behind common assumptions about on-chain data, storage, and standards.
No, the majority of token metadata is stored off-chain. While a token's smart contract and core properties like total supply exist on-chain, descriptive data such as the token's name, symbol, and artwork are typically referenced via a URI (Uniform Resource Identifier) pointing to an off-chain JSON file. This off-chain storage model, used by standards like ERC-721 and ERC-1155, balances cost and flexibility, as storing large data blobs directly on-chain is prohibitively expensive in terms of gas fees. The on-chain component is essentially a pointer; if the off-chain server hosting the JSON file goes down, the metadata becomes inaccessible, a risk mitigated by decentralized storage solutions like IPFS or Arweave.
TECHNICAL DETAILS
Token Metadata
Token metadata provides the descriptive and functional information that defines a digital asset, including its name, symbol, supply, and on-chain behavior. This section answers common technical questions about how metadata is structured, stored, and used across different blockchain standards.
Token metadata is the structured data that describes the properties and characteristics of a fungible or non-fungible token on a blockchain. It provides the essential information needed to identify, display, and interact with the token. Standard metadata fields typically include the token's name, symbol, total supply, decimals, and a link to an off-chain logo or image. For NFTs, metadata is more extensive, often containing a link to a JSON file that defines attributes like the artwork's description, visual assets, and traits. This data is crucial for wallets, explorers, and marketplaces to correctly represent the token to users.
TOKEN METADATA
Frequently Asked Questions (FAQ)
Token metadata defines the properties and characteristics of a digital asset on-chain. This FAQ addresses common questions about its standards, storage, and usage across different blockchain networks.
Token metadata is the structured data that describes the properties and characteristics of a fungible or non-fungible token (NFT) on a blockchain. It typically includes the token's name, symbol, decimals, and a link to an off-chain resource containing more detailed information like images, descriptions, or attributes. For NFTs, this metadata is crucial for defining the unique visual and functional aspects of the digital asset, such as its artwork, traits, and collection details. The metadata itself is often stored off-chain (e.g., on IPFS or a centralized server) for efficiency, with only a URI (Uniform Resource Identifier) pointing to this data stored on the blockchain.
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