zip-archive · shipping · also ZIP file

ZIP archive

A ZIP archive is a container of individually described entries whose local headers and payloads are indexed by a central directory.

Related Observatory article: ZIP archive on hesela.com

ZIP stores per-entry metadata and supports stored or compressed payloads. The local header and central-directory entry contain CRC and size fields; interpreting a listed entry is distinct from reading and checking its payload. [1]

A filename need not identify a unique entry. The Python API accepts a ZipInfo object to select a particular occurrence. A name-keyed inventory can collapse repeated names, changing which bytes are validated or recovered. [2]

On the tested CPython 3.12.3 build, testzip() reopened entries by name and missed a damaged earlier duplicate. Explicit ZipInfo reads detected the CRC error. Six controlled fixtures also showed that the zipfile testing CLI could report corruption while returning exit status 0. These are version-specific observations, not a ZIP format guarantee. [3] [4]

Restoration needs an explicit member-selection rule, complete payload checks and an independent expectation of the intended contents. Retain validation errors separately from process completion and rerun damaged-input controls after changing the reader. [4]

Relations

related

archive-member, backup-manifest, checksum, restore-test

Citations

1. PKWARE ZIP APPNOTE: local headers, central directory and CRC fields, sections 4.3.7 and 4.3.12 (accessed 2026-10-18)
2. Python 3.12 zipfile: ZipInfo selection, testzip and command-line testing (accessed 2026-10-18)
3. CPython issue 156539: testzip skips earlier duplicate members (reported August 2026) (accessed 2026-10-18)
4. Hesela: controlled ZIP entry-identity and CLI-status observations (accessed 2026-10-18)

JSON: /data/terms/zip-archive.json