OPF-029 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 document (OPF)

`OPF-029`

Updated: Nov 3, 2026

EPUBCheck OPF-029 is an error message: “The file "…" does not appear to match the media type …, as specified in the OPF file.” A file's content does not match the media type declared for it in the manifest.

The official message

The file "%1$s" does not appear to match the media type %2$s, as specified in the OPF file.

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 PNG declared as image/jpeg (or the reverse), or a file that was converted without updating the manifest.

How to fix it

Change the media-type in the manifest to the file's real format, or convert the file.

Terms used here

Other OPF messages

OPF-028 Undeclared prefix: "…".
OPF-030 The unique-identifier "…" was not found.
OPF-027 Undefined property: "…".
OPF-031 File listed in reference element in guide was not declared in OPF manifest: ….
OPF-026 Found malformed property value: "…".
OPF-025 Property value list "…" is not allowed, only one value must be specified.

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