Overview
ISO/IEC 21320-1:2015 - Document Container File (Part 1: Core) defines a standardized, interoperable profile for document container files based on the PKWARE Zip File Format (Appnote v6.3.3). The standard specifies the core requirements for both document container files and implementations that produce or consume them, clarifying how Zip-based archives should be used for digital document packaging to improve stability, compatibility and global interoperability.
Key topics and technical requirements
- Zip profile: Document container files are Zip archives conforming to the Appnote (ZIP File Format Specification v6.3.3). The Appnote is interpreted with ISO/IEC annotations to restrict or clarify features.
- Permitted compression: Only stored (method 0) and deflated (method 8) compression are allowed. Deflate MUST follow IETF RFC 1951.
- Encryption & signatures prohibited: Traditional PKWARE encryption, strong encryption, archive decryption headers and Appnote digital-signature constructs are not permitted for container files under this part.
- No splitting/spanning: Archives shall not span multiple volumes or be split into segments.
- ZIP64 limits: ZIP64 extension version 1 is permitted; ZIP64 version 2 is prohibited. The “version needed to extract” shall not exceed 45.
- General purpose bit flags: Bits 0, 4–10 and 12–15 must not be set. Bit 11 should be set and must be set when any filename or comment bytes are > 0x7F; if set, names/comments must be UTF‑8 per ISO/IEC 10646:2014 (Annex D).
- Filenames & Unicode: Any Unicode character is allowed in zip item names per Appnote, but implementers must be aware of:
- Unicode normalization (NFC/NFKC vs NFD) and OS filesystem behavior that can cause name collisions.
- IRI and package-level restrictions (some packages disallow certain characters or Private Use Area code points).
- Interoperability guidance: Annexes provide informal summary, filename interoperability rules and recommended normalizations for XML-based packages.
Applications and who uses it
- Software vendors building document packaging, office suites, EPUB/OCF, digital preservation, content management or archiving systems.
- Developers of tools that create, validate or extract Zip-based document containers.
- Standards bodies and integrators that need a stable, standardized Zip profile to reference (improves cross-platform interoperability).
Related standards
Keywords: ISO/IEC 21320-1, Document Container File, Zip, Appnote, ZIP64, UTF-8, DEFLATE, interoperability, document packaging.
