# w3c/epubcheck

The conformance checker for EPUB publications

Repository: https://github.com/w3c/epubcheck
Canonical: https://ross.abutalabs.com/products/epubcheck
Homepage: https://www.w3.org/publishing/epubcheck/
Language: Java
License: BSD-3-Clause
License Family: permissive
Topics: publishing, digital-publishing, epub, epub3, epubcheck, epub-publications
Last push: 2026-03-01T23:26:20+00:00

## Health v2 (maintenance only)
Score: 59/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 70, release rhythm 21, longevity 100
- inputs: {"age_days": 4706, "days_push": 185, "days_rel": 366, "gap_med": 122.0, "n_releases_24m": 3}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1952, forks 442 (observed 2026-08-28T04:05:58.369541+00:00)

## What it is
EPUBCheck is the official W3C conformance checker for EPUB publications, validating EPUB 2 and EPUB 3 files against the official specifications. It is distributed as a standalone command-line tool and as a Java library for integration into larger publishing systems.

## Use cases
- validate an epub file before submitting it to a retailer
- check epub3 conformance against the official specification
- integrate epub validation into a publishing pipeline
- find errors in an ebook's package metadata and content markup
- batch-check a folder of epub files for defects
- verify internal references and container structure of an epub

## When to choose
- you need the authoritative, spec-compliant EPUB validator used by the publishing industry
- you want a command-line tool or Java library for automated EPUB validation
- you are a content distributor gating ebook acceptance on conformance checks

## When to avoid
- you need a graphical interface and don't want to use third-party GUI wrappers
- you need editorial review like typo or content-quality checking, which EPUBCheck does not do
- you are validating non-EPUB ebook formats such as MOBI or PDF

## Facets
- artifact type: cli-tool
- maturity: stable
- function: testing, parser, developer-tools
- domain: files, developer-tools, documentation
- platform: cross-platform, cli, jvm
- tags: epub, epub3, epub2, validation, conformance-checker, digital-publishing, w3c, java-library, publishing

## Member repositories
- w3c/epubcheck (main) score 59

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:58.369541+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:06:48.168978+00:00, confidence not recorded.
  - readme: https://github.com/w3c/epubcheck (fetched 2026-08-28T04:05:58.369541+00:00, sha 40eede6cf4d4)
  - homepage: https://www.w3.org/publishing/epubcheck/ (fetched 2026-08-29T10:46:31.897667+00:00, sha 9b1e550a45da)
  - site_page: https://www.w3.org/publishing/epubcheck/about (fetched 2026-08-29T10:46:31.900127+00:00, sha 34036ecaa404)
  - site_page: https://www.w3.org/publishing/epubcheck/docs (fetched 2026-08-29T10:46:31.901918+00:00, sha cc7fd51fb822)
  - site_page: https://www.w3.org/publishing/epubcheck/docs/support (fetched 2026-08-29T10:46:31.903527+00:00, sha 5f946d9a4754)
  - site_page: https://www.w3.org/publishing/epubcheck/docs/getting-started (fetched 2026-08-29T10:46:31.905070+00:00, sha 4d3596f88947)
  - site_page: https://www.w3.org/publishing/epubcheck/docs/translating (fetched 2026-08-29T10:46:31.906585+00:00, sha 80c74c2352ca)
  - site_page: https://www.w3.org/publishing/epubcheck/docs/apps-and-tools (fetched 2026-08-29T10:46:31.908421+00:00, sha 299e882925d6)
  - site_page: https://www.w3.org/publishing/epubcheck/about/sponsors (fetched 2026-08-29T10:46:31.912731+00:00, sha f5da62b4b033)
  - site_page: https://www.w3.org/publishing/epubcheck/releases (fetched 2026-08-29T10:46:31.910067+00:00, sha 02db097a04b7)
- Data as of 2026-08-30T08:39:29.467469+00:00.