EPUB Error: Unsupported Image Format (MED-002)

MED-002: Referenced resource "images/photo.tiff" is of a type that is not allowed in this context

What causes this error?

EPUB 3 defines a set of core media types — formats that all compliant reading systems must support. For images, those are JPEG (image/jpeg), PNG (image/png), GIF (image/gif), SVG (image/svg+xml), and WebP (image/webp, added in EPUB 3.3). Any other image format — including TIFF, BMP, HEIC, AVIF, PSD, or EMF — is not in the core media types and triggers MED-002 when referenced in content or declared in the manifest. TIFF files typically arrive from InDesign or Photoshop exports that didn't convert to web formats. HEIC images come from iOS photos imported directly into a manuscript. BMP appears in files converted from older Windows applications. Unlike EMF images (which have a specific fallback mechanism), these formats have no fallback path in the EPUB spec — the only fix is to convert them to a supported format.

How to fix it

  1. Run EPUBCheck to identify every MED-002 error — each one specifies the file and the unsupported image path.
  2. For each unsupported image, convert it to JPEG (for photos and complex images) or PNG (for images with transparency, diagrams, or line art). Use an image editor, export from your source application, or a free converter tool.
  3. If the filename extension changes during conversion (e.g., photo.tiff → photo.jpg), update every reference to the old filename: in the OPF manifest href and media-type, and in any <img src="..."> elements in chapter XHTML files.
  4. Update the manifest media-type attribute to match the new format: media-type="image/jpeg" or media-type="image/png".
  5. Delete the original unsupported format file from the EPUB package, then re-validate with EPUBCheck to confirm no MED-002 errors remain.

Common questions

Is WebP a valid EPUB image format?

WebP (image/webp) was added to the EPUB 3.3 core media types, so it is valid in EPUB 3.3 publications. However, many older e-readers and platforms still run EPUB 3.0 or EPUB 3.2 validators, which do not include WebP in their core media type lists. For maximum compatibility across all platforms and devices, JPEG and PNG remain the safest choices.

My image is an EMF file — is that the same as this error?

EMF is a different case. The EPUB spec allows "foreign" (non-core) resources in the manifest only if a fallback is provided. EMF images trigger a separate "fallback required" error rather than a flat MED-002 rejection. In practice the fix is the same — convert to PNG or JPEG — but the EPUBCheck error code and the spec path that leads to it differ.

Check your EPUB before uploading

The free EPUB Validator catches structure, metadata, and navigation errors — no signup, no Java, runs in the browser.

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Building your EPUB correctly from the start prevents most of these errors before they happen. See the EPUB formatting guide for the full workflow: manuscript cleanup, TOC, front matter, EPUB 3.0 generation, and validation.

Common EPUB errors: EMF image fallback error (foreign resource), Missing alt text on images, Missing manifest resource

Platform rejection guides: Why Apple Books rejects ebooks