Overview

The international vocabulary for blockchain and distributed ledger technologies; second edition published 2024, replacing ISO 22739:2020

ISO 22739:2024 defines the terminology for blockchain and distributed ledger technologies (DLT). It is the reference vocabulary for the whole ISO/TC 307 portfolio: other documents in the series use its definitions rather than repeating them. The second edition was published in 2024 and replaces ISO 22739:2020, which is withdrawn. A further revision is in the early stages of development within ISO/TC 307.

As a vocabulary standard it contains no requirements and cannot be certified against. Its value is coordination: blockchain terminology emerged from overlapping communities — cryptography, distributed systems, financial market infrastructure and cryptocurrency projects — and the same word is often used for materially different things. ISO 22739 resolves those conflicts with agreed, internationally reviewed definitions.

It defines the foundational concepts: distributed ledger, blockchain (a distributed ledger with confirmed blocks organised in an append-only, sequential chain using cryptographic links), distributed ledger system, ledger record, block, transaction, consensus and consensus mechanism, node, genesis block, hash function and cryptographic hash, immutability, and smart contract — the last being a frequent source of misunderstanding, since in the standard's sense it is a computer program stored in a DLT system whose execution enforces the outcome of transactions.

It also standardises the governance and access distinctions that dominate design discussions: permissioned versus permissionless DLT systems, and public versus private DLT systems — two orthogonal axes that are frequently conflated in industry writing. Roles such as DLT user, DLT node operator and DLT service provider are also defined, and these carry across into the reference architecture of ISO 23257.

The practical use of the vocabulary is in procurement documents, technical specifications, regulatory submissions, audit scopes and contracts, where an agreed definition of terms such as "immutable", "permissioned" or "smart contract" removes ambiguity that would otherwise cause disputes.

Companion documents in ISO/TC 307 include ISO 23257 (reference architecture), ISO/TS 23635 (guidelines for governance), ISO/TR 23455 (overview of and interactions between smart contracts in blockchain and DLT systems), ISO/TR 23244 (privacy and personally identifiable information protection) and ISO/TR 23576 (security management of digital asset custodians).

Purpose

To provide an internationally agreed set of definitions for blockchain and distributed ledger technology concepts, so that specifications, contracts, regulation and technical documents use the terms consistently.

Key Benefits

• Provides a single authoritative definition set for blockchain and DLT terminology
• Resolves conflicting industry usage of terms such as smart contract, immutability and consensus
• Distinguishes permissioned/permissionless from public/private, two axes routinely conflated
• Serves as the normative vocabulary for the rest of the ISO/TC 307 portfolio
• Useful in contracts, procurement specifications and regulatory submissions to avoid ambiguity
• Short and accessible compared with full technical specifications
• Neutral with respect to specific platforms, protocols and cryptocurrencies
• Supports consistent audit and assurance scoping for DLT systems
• Updated in 2024 to reflect how the technology and its terminology have matured
• Aids cross-border and cross-industry communication between technical and legal teams

Key Requirements

• Note: ISO 22739 is a vocabulary standard — it contains definitions rather than auditable requirements
• Use the defined terms consistently in specifications, contracts and technical documentation
• Apply the standard's definitions of distributed ledger, blockchain and distributed ledger system
• Use the defined terms for blocks, ledger records, transactions and genesis block
• Apply the defined meanings of consensus and consensus mechanism
• Use the defined distinction between permissioned and permissionless DLT systems
• Use the defined distinction between public and private DLT systems
• Apply the standard's definition of smart contract when specifying or contracting for such functionality
• Use the defined role terms, including DLT user, DLT node operator and DLT service provider
• Refer to ISO 23257 for the architectural elaboration of these concepts
• Reference the current 2024 edition rather than the withdrawn 2020 edition

Who Needs This Standard?

Anyone specifying, procuring, regulating or auditing blockchain and DLT systems — solution architects and developers, legal and contracting teams, standards and policy bodies, financial market participants, and auditors scoping assurance work over distributed ledger platforms.

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