ISO IEC 23736-6-2020 PDF

Full title and description

Information technology — Digital publishing — EPUB 3.0.1 — Part 6: Canonical fragment identifiers. This part defines the EPUB Canonical Fragment Identifier (epubcfi), a standardized fragment identifier syntax for referencing arbitrary locations and simple ranges inside EPUB Publications to enable interoperable linking, location maintenance, annotations and other cross-platform features.

Abstract

This specification (EPUB CFI) defines a structural fragment identifier scheme that can uniquely identify any location or a simple contiguous range within an EPUB Publication. It is designed for interoperability between Reading Systems, to enable document-level linking comparable to the Web, to allow reference without modifying source files, to support efficient resolution and comparison operations, and to provide extensibility for future recovery heuristics.

General information

• Status: Published (International Standard; confirmed).
• Publication date: 19 February 2020 (Edition 1, 2020).
• Publisher: ISO/IEC (developed within ISO/IEC JTC 1/SC 34).
• ICS / categories: 35.240.30 (IT applications in information, documentation and publishing).
• Edition / version: Edition 1 (2020).
• Number of pages: 20.

Scope

Specifies the EPUB Canonical Fragment Identifier (epubcfi) syntax and usage for addressing precise locations and simple ranges inside EPUB 3.0.1 Publications. The scope includes rules for constructing and resolving identifiers, considerations for interoperability across Reading Systems, recovery behavior in the face of parser variations and document revisions, and alignment with W3C best practices for fragment identifiers. The intent is to enable linking, annotation anchoring, reading-location persistence and other cross-application references without modifying content files.

Key topics and requirements

• Definition of the epubcfi syntax for addressing positions and simple ranges within EPUB resources.
• Rules ensuring interoperable references between different Reading Systems and applications.
• Requirements that identifiers identify locations without modifying the underlying document.
• Equality and comparison semantics for fragment identifiers to support sorting and tests without accessing referenced files.
• Performance considerations to enable efficient resolution (e.g., avoid processing entire publication to resolve a reference).
• Guidance for recovery heuristics to handle parser differences and document revisions, and an extensible mechanism for future refinement.
• Conformance with W3C fragid best-practices for fragment identifier structures where applicable.

Typical use and users

Primary users are EPUB implementers and the digital publishing ecosystem: reading-system and e-reader application developers, EPUB tool and conversion software vendors, publishers building EPUB packages, annotation and accessibility tool developers, and archivists or content managers who require robust intra-publication linking and location referencing. Use cases include persistent reading positions, cross-application deep links into book content, annotation anchoring, citation linking and accessibility navigation.

Related standards

Part of the ISO/IEC 23736 series that formalizes EPUB 3.0.1; related parts cover container format, package document, content documents, media overlays, and other EPUB components. The EPUB CFI aligns with Web fragment identifier best practices as described by W3C and complements EPUB packaging and content-part standards used across digital publishing and PDF/archival document standards.

Keywords

EPUB, epubcfi, canonical fragment identifier, digital publishing, fragment identifier, reading system, interoperability, EPUB 3.0.1, annotation anchoring, deep linking

FAQ

Q: What is this standard?

A: ISO/IEC 23736-6:2020 defines the EPUB Canonical Fragment Identifier (epubcfi), a standardized fragment identifier syntax for addressing specific locations and simple ranges inside EPUB Publications to enable robust, interoperable linking and referencing.

Q: What does it cover?

A: It covers the syntax, construction, resolution and recovery considerations for epubcfi URIs, requirements for interoperability between Reading Systems, rules for equality and comparison, performance expectations for resolution, and extensibility for future recovery heuristics.

Q: Who typically uses it?

A: Reading system (e-reader) developers, EPUB authoring and conversion tool vendors, publishers, annotation and accessibility tool developers, and anyone needing precise, persistent intra-publication references in EPUB content.

Q: Is it current or superseded?

A: It was published in February 2020 (Edition 1) and was last reviewed and confirmed in 2025; the ISO record indicates this version remains current.

Q: Is it part of a series?

A: Yes — it is Part 6 of the ISO/IEC 23736 family that standardizes EPUB 3.0.1 (other parts address container format, package document, media overlays, content documents, etc.).

Q: What are the key keywords?

A: EPUB, epubcfi, canonical fragment identifier, digital publishing, fragment identifier, interoperability, reading position, annotation anchoring.