PKG-011 is reported as error by default. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.

EPUBCheck · Package and ZIP container

`PKG-011`

Updated: Nov 3, 2026

EPUBCheck PKG-011 is an error message: “The file name "…" is not allowed to end with ".".” A file name inside the EPUB ends with a full stop, which the EPUB container rules forbid.

The official message

The file name "%1$s" is not allowed to end with ".".

Default severity: Error. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.
EPUBCheck version: 5.4.0

%1$s, %2$s… are filled in with the file, value or element EPUBCheck found.

Typical causes

A file saved without an extension after a name that ends in a dot, or a tool that trimmed the extension.

How to fix it

Give the file a proper extension (for example .xhtml, .jpg or .css).
After renaming, update every reference to the file: the manifest in the package document, links and image sources in the XHTML, and url() references in the CSS.

Terms used here

What is the EPUB container (OCF)?

Other PKG messages

PKG-010 The file name "…" contains spaces, which may create interoperability issues with older reading systems.
PKG-012 The file name "…" contains non-ASCII characters, which might create interoperability issues with older reading systems.
PKG-009 The file name "…" contains characters that are not allowed in OCF file names: ….
PKG-014 The EPUB contains empty directory "…".
PKG-007 The content of the mimetype file must be the string "application/epub+zip"…
PKG-006 Mimetype file entry is missing or is not the first file in the archive.

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EPUBLab.