EPUB FixerKDP upload error scanner

OPF_029 manifest media-type mismatch

Use this when content.opf declares the wrong media type for a real packaged file. Match the manifest entry to the actual file before you retry the EPUB.

Scan EPUB structureSee an example report

The scan shows affected paths and repair decisions. It does not show manuscript text.

Not sure this kind of EPUB should be scanned here? Check unsupported or manual-only EPUB cases.

Scan report titles

  • Manifest media-type does not match the file extension
  • OPF-029 media-type does not match the file
  • The file does not appear to match the media type

Read the scan report

How to decide whether this report item matches OPF_029 manifest media-type mismatch.

Use the report label, affected file, and repair decision together. A matching title alone is not enough if the file path or EPUB structure points to a different problem.

Match the report title.

Look for "Manifest media-type does not match the file extension" or the closest title listed above. If the platform wording is different, keep the original EPUBCheck, KDP, or Kindle Previewer message before choosing a fix.

Check the affected file first.

Use the report's Affected area, Source file, Target file, or Problem type rows before editing content.opf, nav.xhtml, toc.ncx, XHTML, CSS, or image paths.

Follow the repair decision.

Repairable means EPUB Fixer found one clear structural change. Manual review or Not supported means use the source project, formatter, or platform workflow instead of guessing.

Handoff summary

What to send to a formatter if this is not safely repairable.

Copy the report summary instead of rewriting the EPUB from memory. A useful handoff includes the source file, target file or field, original error, repair decision, and next step.

Source file
Target path or field
Original error
Repair decision
Next step

1. Example report output

What the OPF_029 report should show.

A useful report should connect the manifest item to the real packaged file instead of only saying the media type is wrong.

EPUBCheck message

ERROR(OPF-029): OEBPS/content.opf: Item "images/cover.png" does not appear to match the media type image/jpeg.

KDP / Previewer wording

The EPUB package lists a file type in content.opf that does not match the real resource.

EPUB Fixer report

Manifest href images/cover.png is declared as image/jpeg, but the packaged file extension is .png.

Do this next

Change the media-type only if the file path and file type are deterministic and the file is the real packaged asset.

Do not do this

Do not rename the file, swap in a new asset, or guess a different format just to clear OPF_029.

A safe fix keeps the same file and updates only the manifest media-type when the packaged file is already correct.

2. Next step

Choose scan, safe manifest repair, or source export review.

The next step depends on whether the EPUB already contains the right file and only the OPF manifest entry is wrong.

Scan first

You only have the validator message.

Upload the EPUB so the report can show the manifest href, the packaged file path, and the exact media-type mismatch before you edit content.opf.

Matched

Safe repair

The packaged file is clear and only the media type is wrong.

Update the manifest media-type when one existing file clearly maps to one EPUB media type, then validate again.

Manual review

The file itself is unclear or exported incorrectly.

Stop when the asset may need re-export, replacement, or author/formatter judgment instead of a manifest-only correction.

3. Concrete path example

A typical OPF_029 manifest mismatch.

The report should show the same href in content.opf and the real file it points to inside the EPUB.

EPUBCheck:
ERROR(OPF-029): OEBPS/content.opf: Item "images/cover.png" does not appear to match the media type image/jpeg.

Report:
Manifest href: images/cover.png
Declared media-type: image/jpeg
Packaged file: OEBPS/images/cover.png
Detected file type: image/png
Fix decision: safe repair if this is the intended cover image

If the file itself is wrong or missing, the next step is source repair, not a manifest-only change.

Quick decision

Decide whether this is only a manifest mismatch.

A wrong media-type can be a small deterministic fix. It should not turn into renaming files, swapping assets, or guessing the book's intended resource format.

Scan first

You do not know whether the packaged file is correct.

Use the scan to connect the manifest href to the real packaged file before changing content.opf.

Matched

Safe fix

One packaged file maps to one clear EPUB media type.

If the file exists and its extension or detected format is deterministic, update only the manifest media-type and validate again.

Stop

The file itself needs replacement or export changes.

Do not guess when the asset may be the wrong file, the wrong conversion output, or part of a larger packaging problem.

Start here

Check the real file type before changing content.opf.

OPF_029 is about the manifest entry, not about whether the file exists. Start by confirming what file the manifest points to and whether that file is really PNG, JPEG, SVG, CSS, or XHTML.

Matched

What it means

The EPUB package points to a real file, but content.opf describes that file as the wrong resource type. Kindle and EPUBCheck use the OPF manifest to understand whether a file is an image, stylesheet, XHTML document, SVG, font, or another packaged asset.

Matched

Can it be fixed automatically?

EPUB Fixer can help when the file exists, the href is correct, and the resource type is deterministic from the packaged file. A safe fix updates only the manifest media-type and keeps the same file path.

Matched

What to check next

Copy the exact manifest href and declared media-type from content.opf before making any change.

Matched

What not to assume

It should stop for manual review when the asset itself may be wrong, missing, duplicated, or part of a broader export problem. The tool should not swap files, rename assets, or guess a replacement format.

Common situations

Common OPF_029 cases.

Start with the real file type the manifest points to.

Matched

A PNG image is declared as JPEG.

The file exists and the href already points to cover.png, but content.opf still says image/jpeg.

Set media-type to image/png, then validate again.

Matched

An image file has the wrong manifest media type.

The asset exists, but the manifest entry does not match the actual image format or file extension.

Update the manifest entry only if the packaged file is the intended asset.

A stylesheet, XHTML, or SVG file is declared with the wrong type.

The manifest href points to a real packaged file, but the media-type belongs to another resource category.

Correct the OPF media-type only when the file path and resource type are unambiguous.

The file was converted or renamed incorrectly during export.

The extension, packaged file, and actual resource may no longer agree after a source-tool export or manual ZIP edit.

Re-export or replace the source asset when the file itself is wrong, instead of patching content.opf blindly.

The OPF_029 media-type mismatch text

OPF_029: The manifest media type does not match the referenced file.

Where OPF_029 usually appears

EPUBCheck, Kindle Previewer, or KDP finds a manifest item in content.opf whose media-type does not match the actual packaged file or file extension.

What it means

OPF_029 usually means the manifest entry and the packaged file disagree.

The EPUB package points to a real file, but content.opf describes that file as the wrong resource type. Kindle and EPUBCheck use the OPF manifest to understand whether a file is an image, stylesheet, XHTML document, SVG, font, or another packaged asset.

Common causes include an image converted from JPG to PNG without updating content.opf, files renamed after export, manual ZIP edits, assets copied between EPUBs, and source tools that leave an old media-type value in the manifest.

Before you edit

Compare content.opf with the real packaged file.

Do not change media-type just because the extension looks familiar. First confirm the manifest href, the real file extension, and whether the file was renamed, converted, or exported incorrectly.

  1. 1Copy the exact manifest href and declared media-type from content.opf before making any change.
  2. 2Open the packaged file at that href and confirm whether the extension and real file type match the declared media-type.
  3. 3Check whether the mismatch is limited to content.opf or whether the asset itself was exported, renamed, or converted incorrectly.
  4. 4Keep the same href when the packaged file is already correct and only the media-type is wrong.
  5. 5Stop and review the source export when fixing OPF_029 would require replacing the asset, renaming files, or guessing which format the book intended to use.

Why KDP checks it

Why EPUBCheck and Kindle care about the manifest media type.

EPUB 3.3 package rules

The OPF file is the EPUB's map: metadata, file list, reading order, and navigation wiring. KDP and EPUBCheck use it to decide whether the book package is coherent.

EPUBCheck

EPUBCheck checks EPUB 2 and EPUB 3 files against the official rules and reports package, markup, link, and file-reference problems.

Can this be fixed safely?

When a media-type mismatch is safe to repair.

When automatic repair is safe

EPUB Fixer can help when the file exists, the href is correct, and the resource type is deterministic from the packaged file. A safe fix updates only the manifest media-type and keeps the same file path.

When you need manual review

It should stop for manual review when the asset itself may be wrong, missing, duplicated, or part of a broader export problem. The tool should not swap files, rename assets, or guess a replacement format.

Before / after example

Before: content.opf declares images/cover.png as image/jpeg. After: the same manifest item is updated to image/png and the EPUB is validated again. Before: the EPUB contains the wrong exported image file entirely; that should go back to the source project instead of being guessed in place.

Ready to retry?

Scan the EPUB before editing the manifest item.

A scan should show the exact manifest item, the packaged file path, and whether the file type is a simple deterministic mismatch or part of a larger export problem.

Upload EPUB to scan

FAQ

Questions authors ask about OPF_029.

What does OPF_029 media-type mismatch mean?

It means content.opf declares a file as one resource type, such as image/jpeg, while the packaged file looks like another type, such as image/png.

Can EPUB Fixer repair a media-type mismatch automatically?

Yes, but only when the packaged file is already correct and the fix is limited to updating the OPF manifest entry to the deterministic media-type.

Should I rename the file to match the manifest?

Not by default. If the packaged asset is already the intended file, the safer change is usually to fix content.opf. Rename or replace the file only when the source export itself is wrong.

Why can this still fail in KDP if the image opens locally?

Local readers may still show the image, but EPUBCheck and Kindle use the OPF manifest to validate whether the package inventory describes the file correctly.

Related EPUB error guides