This EIP proposes the establishment of a comprehensive metadata standard for Cultural and Historical Asset Tokens (CHATs) on the Ethereum platform. These tokens represent cultural and historical assets such as artwork, artifacts, collectibles, and rare items, providing crucial context and provenance to substantiate their significance and value.

While existing NFT standards ensure the immutability and decentralized ownership of assets on the blockchain, based on our research they do not adequately capture the cultural and historical importance and value of such assets needed for widespread adoption by institutions such as museums. The CHAT standard aims to overcome these limitations by preserving the provenance, history, and evolving context of cultural and historical assets, thus substantiating their value. Furthermore, it incentivises museums, institutions, and asset owners to create tamper-proof records on the blockchain, ensuring transparency and accountability and accelerating adoption of web3 protocols. Additionally, the CHAT standard promotes interoperability with existing metadata standards in the arts and cultural sector, facilitating the search, discovery, and connection of distributed assets.


Preserving context and significance - Provenance and context are crucial for cultural and historical assets. The CHAT standard captures and preserves the provenance and history of these assets, as well as the changing contexts that emerge from new knowledge and information. This context and provenance substantiate the significance and value of cultural and historical assets.

Proof-based preservation - The recent incidents of lost artifacts and data breaches at a number of significant international museums points to a need in reassessing our current record keeping mechanisms. While existing systems mostly operate on trust, blockchain technology offers opportunities to establish permanent and verifiable records in a proof-based environment. Introducing the CHAT standard on the Ethereum platform enables museums, institutions, and owners of significant collections to create tamper-proof records on the blockchain. By representing these valuable cultural and historical assets as tokens on the blockchain, permanent and tamper-proof records can be established whenever amendments are made, ensuring greater transparency and accountability.

Interoperability - The proposed standard addresses the multitude of existing metadata standards used in the arts and cultural sector. The vision is to create a metadata structure specifically built for preservation on the blockchain that is interoperable with these existing standards and compliant with the Open Archives Initiative (OAI) as well as the International Image Interoperability Framework protocol (IIIF).

Search and Discovery - Ownership and history of artworks, artifacts, and historical intellectual properties are often distributed. Although there may never be a fully consolidated archive, a formalized blockchain-based metadata structure enables consolidation for search and discovery of the assets, without consolidating the ownership. For example, an artifact from an archaeological site of the Silk Road can be connected with Buddhist paintings, statues, and texts about the ancient trade route across museum and institutional collections internationally. The proposed CHAT metadata structure will facilitate easy access to these connections for the general public, researchers, scholars, other cultural professionals, brands, media, and any other interested parties.

Currently, the ERC-721 standard includes a basic metadata extension, which optionally provides functions for identifying NFT collections (“name” and “symbol”) and attributes for representing assets (“name,” “description,” and “image”). However, to provide comprehensive context and substantiate the value of tokenized assets, NFT issuers often create their own metadata structures. We believe that the basic extension alone is insufficient to capture the context and significance of cultural and historical assets. The lack of interoperable and consistent rich metadata hinders users’ ability to search, discover, and connect tokenized assets on the blockchain. While connectivity among collections may not be crucial for NFTs designed for games and memberships, it is of utmost importance for cultural and historical assets. As the number and diversity of tokenized assets on the blockchain increase, it becomes essential to establish a consistent and comprehensive metadata structure that provides context, substantiates value, and enables connected search and discovery at scale.


The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119 and RFC 8174.

This EIP extends ERC-721 and ERC-1155 with 48 additional properties to capture the cultural and historical significance of the underlying asset.

Compatible contracts, besides implementing the relevant metadata schemas (“Metadata JSON Schema” for ERC-721 contracts or “Metadata URI JSON Schema” for ERC-1155 contracts), must implement the following metadata interface.

Cultural and Historical Asset Metadata Extension TypeScript Interface

The following TypeScript interface defines the Metadata JSON Schema compatible tokens must conform to:

interface HistoricalAssetMetadata {
    name?: string;                              // Name of the CHAT
    description?: string;                       // Full description of the CHAT to provide the cultural and historical
                                                // context
    image?: string;                             // A URI pointing to a resource with mime type image/* to serve as the
                                                // cover image of the CHAT
    attributes?: CHATAttribute[];               // A list of attributes to describe the CHAT. Attribute object may be
                                                // repeated if a field has multiple values
    attributesExt?: ExtendedCHATAttribute[];    // A list of extended attributes to describe the CHAT, not to be
                                                // displayed. Attribute object may be repeated if a field has
                                                // multiple values

type CHATAttribute =
    { trait_type: "Catalogue Level", value: string }
    | { trait_type: "Publication / Creation Date", value: string }
    | { trait_type: "Creator Name", value: string }
    | { trait_type: "Creator Bio", value: string }
    | { trait_type: "Asset Type", value: string }
    | { trait_type: "Classification", value: string }
    | { trait_type: "Materials and Technology", value: string }
    | { trait_type: "Subject Matter", value: string }
    | { trait_type: "Edition", value: string }
    | { trait_type: "Series name", value: string }
    | { trait_type: "Dimensions Unit", value: string }
    | { trait_type: "Dimensions (height)", value: number }
    | { trait_type: "Dimensions (width)", value: number }
    | { trait_type: "Dimensions (depth)", value: number }
    | { trait_type: "Inscriptions / Marks", value: string }
    | { trait_type: "Credit Line", value: string }
    | { trait_type: "Current Owner", value: string }
    | { trait_type: "Provenance", value: string }
    | { trait_type: "Acquisition Date", value: string }
    | { trait_type: "Citation", value: string }
    | { trait_type: "Keyword", value: string }
    | { trait_type: "Copyright Holder", value: string }
    | { trait_type: "Bibliography", value: string }
    | { trait_type: "Issuer", value: string }
    | { trait_type: "Issue Timestamp", value: string }
    | { trait_type: "Issuer Description", value: string }
    | { trait_type: "Asset File Size", value: number }
    | { trait_type: "Asset File Format", value: string }
    | { trait_type: "Copyright / Restrictions", value: string }
    | { trait_type: "Asset Creation Geo", value: string }
    | { trait_type: "Asset Creation Location", value: string }
    | { trait_type: "Asset Creation Coordinates", value: string }
    | { trait_type: "Relevant Date", value: string }
    | { trait_type: "Relevant Geo", value: string }
    | { trait_type: "Relevant Location", value: string }
    | { trait_type: "Relevant Person", value: string }
    | { trait_type: "Relevant Entity", value: string }
    | { trait_type: "Asset Language", value: string }
    | { trait_type: "Is Physical Asset", value: boolean }

type ExtendedCHATAttribute =
    { trait_type: "Asset Full Text", value: string }
    | { trait_type: "Exhibition / Loan History", value: string }
    | { trait_type: "Copyright Document", value: string }
    | { trait_type: "Provenance Document", value: string }
    | { trait_type: "Asset URL", value: string }
    | { trait_type: "Copyright Document of Underlying Asset", value: string }

CHATAttribute Description

trait_type description
Catalogue Level An indication of the level of cataloging represented by the record, based on the physical form or intellectual content of the material
Publication / Creation Date Earliest possible creation date of the underlying asset in ISO 8601 date format
Creator Name The name, brief biographical information, and roles (if necessary) of the named or anonymous individuals or corporate bodies responsible for the design, production, manufacture, or alteration of the work, presented in a syntax suitable for display to the end-user and including any necessary indications of uncertainty, ambiguity, and nuance. If there is no known creator, make a reference to the presumed culture or nationality of the unknown creator
Creator Bio The brief biography or description of creator
Asset Type The type of the underlying asset
Classification Classification terms or codes are used to place a work of art or architecture in a useful organizational scheme that has been devised by a repository, collector, or other person or entity. Formal classification systems are used to relate a work of art or architecture to broader, narrower, and related objects. Classification terms group similar works together according to varying criteria
Materials and Technology The materials and/or techniques used to create the physical underlying asset
Subject Matter Indexing terms that characterize in general terms what the work depicts or what is depicted in it. This subject analysis is the minimum required. It is recommended to also list specific subjects, if possible
Edition Edition of the original work
Series Name The name of the series the asset is a part of
Dimensions Unit Unit of the measurement of the dimension of the asset
Dimensions (height) Height of the underlying asset
Dimensions (width) Width of the underlying asset
Dimensions (depth) Depth of the underlying asset
Credit Line Crediting details of the source or origin of an image or content being used publicly. The credit line typically includes important details such as the name of the museum, the title or description of the artwork or object, the artist’s name (if applicable), the date of creation, and any other relevant information that helps identify and contextualize the work
Inscriptions / Marks A description of distinguishing or identifying physical markings, lettering, annotations, texts, or labels that are a part of a work or are affixed, applied, stamped, written, inscribed, or attached to the work, excluding any mark or text inherent in materials (record watermarks in MATERIALS AND TECHNIQUES)
Current Owner Name of the current owner
Provenance Provenance provides crucial information about the artwork’s authenticity, legitimacy, and historical significance. It includes details such as the names of previous owners, dates of acquisition, locations where the artwork or artifact resided, and any significant events or transactions related to its ownership
Acquisition Date The date on which the acquirer obtained the asset
Citation Citations of the asset in publications, journals, and any other medium
Keyword Keywords that are relevant for researchers
Copyright Holder Copyright holder of the underlying asset
Bibliography Information on where this asset has been referenced, cited, consulted, and for what purpose
Issuer Issuer of the token
Issue Timestamp Date of token creation
Issuer Description Brief description of the issuing party
Asset File Size Size of the digital file of the underlying asset in bytes
Asset File Format The physical form or the digital format of the underlying asset. For digital format, a MIME type should be specified
Copyright / Restrictions The copyright status the work is under
Asset Creation Geo Country, subdivision, and city where the underlying asset was created. Reference to ISO 3166-2 standard for the short name of the country and subdivision. Utilize the official name for the city if it is not covered in the ISO subdivision
Asset Creation Location Specific cities and named locations where the underlying asset was created
Asset Creation Coordinates Coordinates of the location where the underlying asset was created
Relevant Date Dates, in ISO 8601 date format, referenced in, and important to the significance of the CHAT
Relevant Geo Country, subdivision, and city CHATs are referenced and important to the significance of the CHAT. Reference to ISO 3166-2 standard for the short name of the country and subdivision. Utilize the official name for the city if it is not covered in the ISO subdivision
Relevant Location Specific cities and named locations referenced in, and important to the significance of the CHAT
Relevant Person Individuals referenced in, and important to the significance of the CHAT
Relevant Entity Entities referenced in, and important to the significance of the CHAT
Asset Language Languages used in the underlying asset. Reference to ISO 639 for code or macrolanguage names
Is Physical Asset Flags whether the asset is tied to a physical asset

ExtendedCHATAttribute Description

trait_type description
Asset Full Text The full text in the underlying asset of the CHAT
Exhibition / Loan History Including exhibition/loan description, dates, title, type, curator, organizer, sponsor, venue
Copyright Document A URI pointing to the legal contract CHATs outlines the copyright of the underlying asset
Provenance Document A URI pointing to the existing provenance record documents of the underlying asset
Asset URL A URI pointing to a high-quality file of the underlying asset
Copyright Document of Underlying Asset A URI pointing to legal document outlining the rights of the token owner. Specific dimensions include the right to display a work via digital and physical mediums, present the work publicly, create or sell copies of the work, and create or sell derivations from the underlying asset


To illustrate the use of the CHAT metadata extension, we provide an example of a CHAT metadata JSON file for the famous Japanese woodblock print “Under the Wave off Kanagawa” by Katsushika Hokusai, which is currently held by the Art Institute of Chicago.

The metadata format is compatible with the ERC-721 and OpenSea style metadata format.

  "name": "Under the Wave off Kanagawa (Kanagawa oki nami ura), also known as The Great Wave, from the series “Thirty-Six Views of Mount Fuji (Fugaku sanjūrokkei)",
  "description": "Katsushika Hokusai’s much celebrated series, Thirty-Six Views of Mount Fuji (Fugaku sanjûrokkei), was begun in 1830, when the artist was 70 years old. This tour-de-force series established the popularity of landscape prints, which continues to this day. Perhaps most striking about the series is Hokusai’s copious use of the newly affordable Berlin blue pigment, featured in many of the compositions in the color for the sky and water. Mount Fuji is the protagonist in each scene, viewed from afar or up close, during various weather conditions and seasons, and from all directions.\n\nThe most famous image from the set is the “Great Wave” (Kanagawa oki nami ura), in which a diminutive Mount Fuji can be seen in the distance under the crest of a giant wave. The three impressions of Hokusai’s Great Wave in the Art Institute are all later impressions than the first state of the design.",
  "image": "ipfs://bafybeiav6sqcgzxk5h5afnmb3iisgma2kpnyj5fa5gnhozwaqwzlayx6se",
  "attributes": [
    { "trait_type": "Publication / Creation Date", "value": "1826/1836" },
    { "trait_type": "Creator Name", "value": "Katsushika Hokusai" },
    { "trait_type": "Creator Bio", "value": "Katsushika Hokusai’s woodblock print The Great Wave is one of the most famous and recognizable works of art in the world. Hokusai spent the majority of his life in the capital of Edo, now Tokyo, and lived in a staggering 93 separate residences. Despite this frenetic movement, he produced tens of thousands of sketches, prints, illustrated books, and paintings. He also frequently changed the name he used to sign works of art, and each change signaled a shift in artistic style and intended audience." },
    { "trait_type": "Asset Type", "value": "Painting" },
    { "trait_type": "Classification", "value": "Arts of Asia" },
    { "trait_type": "Materials and Technology", "value": "Color woodblock print, oban" },
    { "trait_type": "Subject Matter", "value": "Asian Art" },
    { "trait_type": "Subject Matter", "value": "Edo Period (1615-1868)" },
    { "trait_type": "Subject Matter", "value": "Ukiyo-e Style" },
    { "trait_type": "Subject Matter", "value": "Woodblock Prints" },
    { "trait_type": "Subject Matter", "value": "Japan 1800-1900 A.D." },
    { "trait_type": "Edition", "value": "1" },
    { "trait_type": "Series name", "value": "Thirty-Six Views of Mount Fuji (Fugaku sanjûrokkei)" },
    { "trait_type": "Dimensions Unit", "value": "cm" },
    { "trait_type": "Dimensions (height)", "value": 25.4 },
    { "trait_type": "Dimensions (width)", "value": 37.6 },
    { "trait_type": "Inscriptions / Marks", "value": "Signature: Hokusai aratame Iitsu fude" },
    { "trait_type": "Inscriptions / Marks", "value": "Publisher: Nishimura-ya Yohachi" },
    { "trait_type": "Credit Line", "value": "Clarence Buckingham Collection" },
    { "trait_type": "Current Owner", "value": "Art Institute of Chicago" },
    { "trait_type": "Provenance", "value": "Yamanaka, New York by 1905" },
    { "trait_type": "Provenance", "value": "Sold to Clarence Buckingham, Chicago by 1925" },
    { "trait_type": "Provenance", "value": "Kate S. Buckingham, Chicago, given to the Art Institute of Chicago, 1925." },
    { "trait_type": "Acquisition Date", "value": "1925" },
    { "trait_type": "Citation", "value": "James Cuno, The Art Institute of Chicago: The Essential Guide, rev. ed. (Art Institute of Chicago, 2009) p. 100." },
    { "trait_type": "Citation", "value": "James N. Wood, The Art Institute of Chicago: The Essential Guide, rev. ed. (Art Institute of Chicago, 2003), p. 86." },
    { "trait_type": "Citation", "value": "Jim Ulak, Japanese Prints (Art Institute of Chicago, 1995), p. 268." },
    { "trait_type": "Citation", "value": "Ukiyo-e Taikei (Tokyo, 1975), vol. 8, 29; XIII, I." },
    { "trait_type": "Citation", "value": "Matthi Forrer, Hokusai (Royal Academy of Arts, London 1988), p. 264." },
    { "trait_type": "Citation", "value": "Richard Lane, Hokusai: Life and Work (London, 1989), pp. 189, 192." },
    { "trait_type": "Copyright Holder", "value": "Public domain" },
    { "trait_type": "Copyright / Restrictions", "value": "CC0" },
    { "trait_type": "Asset Creation Geo", "value": "Japan" },
    { "trait_type": "Asset Creation Location", "value": "Tokyo (Edo)" },
    { "trait_type": "Asset Creation Coordinates", "value": "36.2048° N, 138.2529° E" },
    { "trait_type": "Relevant Date", "value": "18th Century" },
    { "trait_type": "Relevant Geo", "value": "Japan, Chicago" },
    { "trait_type": "Relevant Location", "value": "Art Institute of Chicago" },
    { "trait_type": "Relevant Person", "value": "Katsushika Hokusai" },
    { "trait_type": "Relevant Person", "value": "Yamanaka" },
    { "trait_type": "Relevant Person", "value": "Clarence Buckingham" },
    { "trait_type": "Relevant Person", "value": "Kate S. Buckingham" },
    { "trait_type": "Relevant Entity", "value": "Art Institute of Chicago, Clarence Buckingham Collection" },
    { "trait_type": "Asset Language", "value": "Japanese" },
    { "trait_type": "Is Physical Asset", "value": true }


Choosing to Extend Off-Chain Metadata JSON Schema over On-Chain Interface

Both the ERC-721 and ERC-1155 provide natural extension points in the metadata JSON file associated with NFTs to supply enriched datasets about the underlying assets.

Providing enriched datasets through off-chain metadata JSON files allows existing NFT contracts to adopt the new metadata structure proposed in this EIP without upgrading or migrating. The off-chain design enables flexible and progressive enhancement of any NFT collections to adopt this standard gradually. This approach allows NFT collections to be deployed using already-audited and battle-tested smart contract code without creating or adapting new smart contracts, reducing the risk associated with adopting and implementing a new standard.

Capturing Attributes Extensions in attributes and attributesExt properties

In the design of the Cultural and Historical Asset Token (CHAT) metadata extension, we have made a deliberate choice to capture the metadata attributes between two main properties: attributes and attributesExt. This division serves two distinct purposes while ensuring maximum compatibility with existing NFT galleries and marketplaces.

1. attributes Property

The attributes property contains core metadata attributes that are integral to the identity and categorization of CHATs. These attributes are meant to be readily accessible, displayed, and searchable by NFT galleries and marketplaces. By placing fundamental details such as the CHAT’s name, description, image, and other key characteristics in attributes, we ensure that these essential elements can be easily presented to users, collectors, and researchers. This approach allows CHATs to seamlessly integrate with existing NFT platforms and marketplaces without requiring major modifications.

2. attributesExt Property

The attributesExt property, on the other hand, is dedicated to extended attributes that provide valuable, in-depth information about a CHAT but are not typically intended for display or search within NFT galleries and marketplaces. These extended attributes serve purposes such as archival documentation, provenance records, and additional context that may not be immediately relevant to a casual observer or collector. By isolating these extended attributes in attributesExt, we strike a balance between comprehensiveness and user-friendliness. This approach allows CHAT creators to include rich historical and contextual data without overwhelming the typical user interface, making the extended information available for scholarly or specialized use cases.

This division of attributes into attributes and attributesExt ensures that the CHAT standard remains highly compatible with existing NFT ecosystems, while still accommodating the specific needs of cultural and historical assets. Users can enjoy a seamless experience in browsing and collecting CHATs, while researchers and historians have access to comprehensive information when required, all within a framework that respects the practicalities of both user interfaces and extended data documentation.

Backwards Compatibility

This EIP is fully backward compatible with ERC-721 and ERC-1155.

Security Considerations

NFT platforms and systems working with Cultural and Historical Asset Metadata JSON files are recommended to treat the files as client-supplied data and follow the appropriate best practices for processing such data.

Specifically, when processing the URI fields, backend systems should take extra care to prevent a malicious issuer from exploiting these fields to perform Server-Side Request Forgery (SSRF).

Frontend or client-side systems are recommended to escape all control characters that may be exploited to perform Cross-Site Scripting (XSS).

Processing systems should manage resource allocation to prevent the systems from being vulnerable to Denial of Service ( DOS) attacks or circumventing security protection through arbitrary code exceptions. Improper processing of variable data, such as strings, arrays, and JSON objects, may result in a buffer overflow. Therefore, it is crucial to allocate resources carefully to avoid such vulnerabilities.

The metadata JSON files and the digital resources representing both the token and underlying assets should be stored in a decentralized storage network to preserve the integrity and to ensure the availability of data for long-term preservation.

Establishing the authenticity of the claims made in the Metadata JSON file is beyond the scope of this EIP, and is left to future EIPs to propose an appropriate protocol.

Copyright and related rights waived via CC0.