Add Cover to EPUB

Add Cover to EPUB sets or swaps the cover image inside an existing EPUB without rebuilding the book. The most natural fit is self-publishing prep: an author or small press who exported an EPUB from Word, Vellum, Calibre, or an InDesign workflow and now needs the right artwork in place before uploading to Kindle Direct Publishing, Apple Books, Kobo, or a personal store. If a file already has a cover, the tool detects it and replaces it; if none is present, it adds one.

It also suits everyday e-reader housekeeping. Sideloaded EPUBs, public-domain downloads, and older conversions often show a blank or generic spine in your library; dropping in a proper cover gives them a real thumbnail in Apple Books, Kobo, KOReader, or Calibre. For teams producing internal handbooks, reports, or course material as EPUB, it is a quick way to brand a finished file with the correct front image without touching the manuscript text.

The flow is deliberately ordered. First drop the .epub so the tool can open it (it reads the container, OPF, and metadata in the browser) and confirm the book title. A status line then tells you whether a cover is already present and will be replaced, or whether a new one will be added. Next, choose a cover image through the file picker; a live preview appears. Pressing Add cover to EPUB writes the new file and gives you a download named after the original with a -with-cover suffix.

Cover images can be JPG, PNG, or WebP, and the image type is taken from the file extension. The tool rewrites the package so both EPUB 2 and EPUB 3 readers find the cover: it stores the image beside the OPF, registers it in the manifest with the cover-image property, and writes the legacy meta name=cover reference. It does not resize, crop, recompress, or convert your image, and it does not generate a styled HTML cover page; it points the existing cover machinery at the file you supply. DRM-protected EPUBs are detected and refused, since they cannot be modified. Everything runs locally in your browser, with nothing uploaded and nothing retained once the tab closes.

On-screen size guidance is provided for reference: roughly 1600x2560 (2:3) for Kindle and Kobo, about 1400x1873 minimum for Apple Books, and 2000x3000 for a universal master.

Because the image is embedded exactly as given, the result is only as good as your file. A small, blurry, or oddly proportioned image will look the same inside the EPUB, and a heavy uncompressed PNG will inflate the book's size. The format is read from the extension, so a file mislabeled (for example a PNG saved as .jpg) can confuse strict readers; export cleanly from your editor rather than renaming. Aim for the 2:3 portrait ratio in the guidance to avoid letterboxing on store thumbnails.

A few structural caveats: the tool relies on a valid EPUB with a readable OPF, so corrupted, non-standard, or DRM-locked files will not process. It updates the cover references but does not create or fix an in-book cover page that some older EPUB 2 readers display as the first page, and it leaves the rest of the manifest untouched. If a store later rejects your upload, that is usually a separate cover-art policy or pixel-size requirement on their side, not a fault in the embedded file.

Open the downloaded -with-cover.epub in a real reader rather than trusting the preview alone. Confirm the new cover shows as the library thumbnail and as the opening image, that it is sharp at thumbnail size, and that the orientation and aspect ratio are correct. Check the book still opens to the right first chapter, and glance at the final file size to be sure your image did not bloat it. Testing in two readers, such as Apple Books or Kobo plus Calibre, catches viewer-specific quirks.

For a title going to a paid store or any official, contracted, or rights-sensitive release, treat this as a convenience step and verify manually. Re-open the file, validate it against the target platform's cover specifications, and run it through that store's own preview or an EPUB validator before publishing, so you confirm the artwork, dimensions, and licensing meet their requirements on the record.