# EPUBCheck OPF-037: deprecated media type, how to fix it

Source: https://epubcc.com/epubcheck/opf-037/ (updated 2026-11-04)

EPUBCheck OPF-037 is a warning message: “Found deprecated media-type "…".” An EPUB 2 manifest uses a deprecated media type, which EPUBCheck names. In EPUB 2 these are the old OEB types such as text/x-oeb1-document, kept only for compatibility with very old publications.

- Official message (EPUBCheck 5.4.0): Found deprecated media-type "%1$s".
- Default severity: Warning

## Typical causes

- A package document carried over from an OEBPS 1.x publication.
- A tool that still writes the old OEB media types.
- Manifests copied from very old books.

## How to fix it

1. Find the manifest item EPUBCheck points to.
2. Change text/x-oeb1-document to application/xhtml+xml, and text/x-oeb1-css to text/css.
3. Make sure the files really are XHTML and CSS; old OEB documents may need cleaning before they validate.

## When it's not this

If the deprecated type is text/html, EPUBCheck reports OPF-035 instead.

## Sources

- EPUBCheck 5.4.0 message texts (MessageBundle.properties, w3c/epubcheck on GitHub): https://github.com/w3c/epubcheck/blob/v5.4.0/src/main/resources/com/adobe/epubcheck/messages/MessageBundle.properties (read 2026-11-04)

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