Kindle EPUB Checker

This tool is a pre-upload review step for authors and small publishers preparing an EPUB for Amazon KDP. You run it after your manuscript is exported as EPUB but before you submit to Kindle, so you can catch the issues that commonly surface during Amazon's conversion rather than discovering them mid-upload. It reads one EPUB at a time and produces a Kindle readiness report listing what passed and what needs attention.

It genuinely fits the e-reader and publishing workflow: a self-publisher finalizing a novel, a non-fiction author checking that the table of contents and cover meet Kindle expectations, or someone re-uploading a corrected edition who wants to confirm the file is clean. It also helps when you have received an EPUB from a designer or conversion service and want an independent look at the cover ratio, metadata, and internal links before trusting it.

It is not a general document converter, a writing tool, or a KDP submission portal. If your manuscript is still in Word, PDF, or another format, convert it to EPUB first and bring the EPUB here. The checker reports on readiness; it does not upload, publish, or distribute anything on your behalf.

The flow is simple: select or drop your EPUB file into the tool, let it process in your browser, and read the resulting report. Everything runs locally — the file is opened and parsed in the browser tab, nothing is uploaded to a server, and nothing is stored once you close the tab. That matters for unpublished manuscripts you do not want leaving your machine.

The report reviews the areas that most often cause Kindle problems: cover image presence, size, and aspect ratio; metadata completeness such as title and author; table of contents structure and navigation; internal links; embedded image sizes; and overall file size. For each item it flags, it points you toward an actionable fix rather than just marking a pass or fail. Input is EPUB; output is the on-screen readiness report you can act on.

Honest scope: this is a checker, not an editor or converter. It does not rewrite your EPUB, regenerate a cover, repair broken markup, or produce AZW3 or KFX files. For changes, you would use a dedicated editor or a cover/metadata tool, then re-run this check to confirm the fixes held.

The most important caveat: this tool is not officially endorsed by Amazon. It checks against common, well-known Kindle requirements and compatibility issues, but Amazon's conversion pipeline can still raise problems this checker does not see. Treat a clean report as a strong pre-check, not a promise that KDP will accept the file without comment.

A frequent mistake is assuming AZW3 or KFX quality is something this tool controls — it is not. Final rendering on Kindle depends on Amazon's internal converter, so a passing EPUB can still display differently once Amazon processes it. Another pitfall is running the check on an outdated export: if you fixed something in your authoring tool, re-export the EPUB and re-run the checker so the report reflects the file you will actually upload.

Also remember the checker reports on structure and technical readiness, not on content correctness. It will not catch typos, formatting choices that are valid but ugly, mislabeled chapters, or a cover that is technically fine but visually wrong. Those still need your own eyes.

Work through the report top to bottom. Confirm the cover is present and its dimensions and ratio are within the flagged range; verify the title and author metadata are filled in and correct; check that the table of contents is detected and its entries match your actual chapters; and look at the file-size and image notes to make sure nothing is oversized. Where the report suggests a fix, apply it in your editing tool, then re-run the check to verify the warning is gone.

After the technical items pass, do a short manual pass that the tool cannot do for you: open the EPUB in a reader, tap through the TOC links, scan a few chapters on a phone-sized screen, and confirm the cover looks right at thumbnail size. The checker tells you the file is structurally ready; only your own review confirms it reads the way you intend.

Because this is a publishing decision with commercial stakes, treat the report as guidance rather than a final clearance. For anything where presentation or rights matter, verify against Amazon KDP's current official requirements and, if needed, rely on KDP's own previewer before publishing — this tool is a pre-check, not the authority.