# EPUBCheck OPF-090: older media type used, how to fix it

Source: https://epubcc.com/epubcheck/opf-090/ (updated 2026-11-04)

EPUBCheck OPF-090 is a usage message: “It is encouraged to use MIME media type "…" instead of "…".” The manifest uses an older media type where a newer one is preferred; EPUBCheck names both. It is a usage note (shown with -u): the older type is still accepted.

- Official message (EPUBCheck 5.4.0): It is encouraged to use MIME media type "%1$s" instead of "%2$s".
- Default severity: Usage

## Typical causes

- Fonts declared as application/vnd.ms-opentype or application/font-woff instead of font/otf or font/woff.
- Manifests written before the current media types were registered.
- Tools that still write the older names.

## How to fix it

1. Read the two media types in the message.
2. Change the manifest item's media-type to the one EPUBCheck suggests.
3. The file itself does not change; nothing else needs updating.

## When it's not this

If the declared type does not match the file at all, that is OPF-029.

## Sources

- EPUB 3.3, §3.2 Core media types: https://www.w3.org/TR/epub-33/#sec-core-media-types (read 2026-11-04)

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EpubCC.