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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallA clean local check does not guarantee that a retailer will accept your EPUB. The store may have tested a different file, used a different validator or version, or flagged something its own conversion pipeline cares about. A mismatch is a reason to compare the two reports line by line. It does not show that either tool is wrong.
This article can’t say what your 17 errors are. The count is the only detail known: no store, validator, version, error codes or message text came with it. What follows is a procedure that turns “17 errors” into a classified list you can fix, and it avoids guessing at causes.
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EPUB Validator & Fixer | Buy on Amazon |
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Why one passing check proves less than it seems
W3C describes EPUBCheck as “the official conformance checker for EPUB publications.” It supports EPUB 2 and EPUB 3 and examines the container structure, package description and metadata, content markup, and the consistency of internal references. The same documentation says “EPUBCheck cannot play an editorial role”: it won’t catch typos or judge whether an image is appropriate.
Retailers add their own layers. Amazon KDP, for example, says it accepts EPUB files that meet the Kindle Publishing Guidelines. It recommends checking a conversion in Kindle Previewer before upload, and it runs an upload conversion with an Online Previewer quality check. Those steps concern how the book converts and displays on Kindle. They are not an independent test of EPUB specification conformance. Retailers also commonly use EPUBCheck in their workflow, but a successful local run doesn’t tell you which version, options or file the store used.
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Several things can therefore differ between your check and the store’s:
- the tool and its version;
- the rule set being applied (EPUB specification versus retailer requirements);
- the scope (the whole package versus a single document);
- the file itself (the one you checked versus the one uploaded);
- the kind of problem (conformance, conversion, display or accessibility).
Step-by-step: from “17 errors” to a fixed upload
1. Preserve the evidence
Save the full store report and the exact EPUB you uploaded. Note the retailer and territory if relevant, the validator name and version if the report shows them, the upload date and the filename. Record a checksum too (for example, run sha256sum yourbook.epub on Linux or macOS). A revised EPUB with the same filename is a different test artifact, and a checksum is the only reliable way to tell them apart.
2. Read all 17 findings, not just the first
For each entry, write down the severity, code, resource path, line and column if present, and the full message. EPUBCheck’s own output uses these fields, and its summary reports counts of fatal errors, errors, warnings and informational messages. Do not treat the entries as equally serious. A fatal error or error is a different matter from a warning. Seventeen entries may also be one underlying defect repeated across many files.
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3. Validate the complete EPUB with a recorded version
Run the official EPUBCheck distribution against the finished .epub package, not an extracted XHTML or CSS file, because some checks depend on the whole publication. A typical command-line run looks like this:
java -jar epubcheck.jar yourbook.epubNote the version it prints. The W3C release page lists EPUBCheck 5.3.0, dated 2025-09-01, for checking EPUB 3.3 conformance. Newer releases may have superseded it, so check the official release page for the current one. If the store’s report names a validator version, run that version as well, since rules and messages change between releases.
4. Compare finding by finding
Build a table with one row per store finding and match it to a local finding by message code, file path, location and meaning:
| Outcome of the comparison | What it suggests | Next action |
|---|---|---|
| Same code and location appear locally | A genuine conformance problem your earlier check missed, perhaps through a different version, scope or file | Fix in the source |
| Local run is clean, store flags the same file | A retailer-specific rule, a different validator version, or conversion behaviour | Read the store’s guidelines for that message; try the store’s preview tool |
| Store finding refers to a resource you don’t recognise | You may have uploaded a different build than the one you checked | Compare checksums |
| Finding concerns appearance or layout | Rendering or conversion issue, not necessarily a conformance error | Inspect the converted preview |
| Finding concerns accessibility | A separate quality dimension | Run an accessibility checker |
Which row applies to each finding can only be settled with the actual report. Don’t assume a retailer is using a different standard unless the messages show it.
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Correct the HTML, CSS, package metadata, navigation or referenced files in your authoring source, then export a new EPUB. Hand-editing the converted output or the preview doesn’t help if the upload still contains the defect. KDP says that when an issue isn’t highlighted in its side panel, you should edit the original source file and upload it again.
6. Rerun both checks and look at the book
Revalidate the rebuilt EPUB, upload it, and review the store’s preview or quality report. KDP offers Kindle Previewer, a free desktop program that opens EPUB files, and an Online Previewer as a last check inside KDP. Look at the result on representative screen sizes and orientations. Amazon’s QA standards also recommend reviewing accessibility, and for EPUBs they point to DAISY’s ACE accessibility checker.
7. Keep a small release record
Store the final file’s checksum, the checker versions, both reports and any retailer-specific result. If a later upload behaves differently, you can then tell whether the file, the checker or the retailer’s workflow changed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Reading an EPUBCheck message
A finding gives a severity, a code, a location and explanatory text. The official guide’s example is an error where a manifest item refers to a file that cannot be found. The code identifies the rule, the location tells you where to look, and the text says what was expected. Search the code in the EPUBCheck documentation or in your report rather than relying on the first sentence of the message alone.
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- The store or distributor, and the territory if it matters.
- The validator name and version, if the report shows them.
- All 17 findings with codes, paths and locations, copied in full.
- Your own EPUBCheck version and complete output for the same file.
- The tool you use to produce the EPUB and its export settings.
With that, the findings can be classified. Without it, any specific diagnosis would be speculation.
Frequently Asked Questions
Does passing EPUBCheck guarantee a retailer will accept my book?
No. EPUBCheck establishes conformance to the EPUB specifications. Retailers also describe their own accepted formats, conversion and preview steps, and they may use a different version or a different file than the one you tested.
Is the store’s validator wrong if my local check is clean?
Not necessarily. First confirm that both tested the same file by comparing checksums. Then compare the tool versions and the codes and locations of each finding.
Quick Recap
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