# EPUBCheck RSC-032: Fallback must be provided for foreign…

Source: https://epublab.com/epubcheck/rsc-032/ (updated 2026-11-03)

EPUBCheck RSC-032 is an error message: “Fallback must be provided for foreign resources, but found none for resource "…" of type "…".” A resource in a format reading apps are not required to support (a foreign resource) is used without a fallback in a core format.

- Official message (EPUBCheck 5.4.0): Fallback must be provided for foreign resources, but found none for resource "%1$s" of type "%2$s".
- Default severity: Error

## Typical causes

- Images in TIFF, BMP or another non-core format referenced directly from the content.

## How to fix it

- Convert the resource to a core media type (for images: JPEG, PNG, GIF, WebP or SVG).
- Or provide a fallback: a manifest fallback attribute, or a picture or object element with an alternative.

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