How Should Designers Format Covers For Sigil Epub?

Love this — designing covers for Sigil EPUBs is such a satisfying little craft, and I always geek out over the tiny details that make a book feel professional on any reader. First off, think pixels not inches: aim for a portrait aspect ratio around 1.6:1 (height:width). A practical baseline I use is about 1600 px tall by 1000 px wide as a minimum; if you want to future-proof for high-density screens, 2400 x 1500 or even 3200 x 2000 is fine as long as you manage file size. Use sRGB color profile, export photographic covers as high-quality JPEG and illustrations or images needing transparency as PNG. Keep the file optimized — try to keep the cover image under about 1 MB for distribution friendliness, using 70–85% JPEG quality and tools to strip unnecessary metadata. Also design with the thumbnail in mind: most people will first see a 150–300 px tall thumbnail, so prioritize bold composition, clear focal point, and large, readable type for title/author text.

On the technical side, Sigil makes it pretty straightforward once you know the steps. Add your image to the book (drag it into the Book Browser or use File -> Add -> Existing Files), and then include a simple XHTML cover page that displays it. I like to create a file called 'cover.xhtml' with a single tag referencing the image in an images folder and CSS that uses max-width:100%; height:auto; display:block; margin:auto; to keep it responsive. In the package document (content.opf) you should ensure the cover image is listed in the manifest and properly marked: for EPUB 3 give the image manifest item the property 'cover-image' (for example, ). For EPUB 2 compatibility also include a metadata meta tag like . Don’t forget to put the cover XHTML as the first spine item so readers that show the first spine file as the initial page display your cover. Sigil’s Metadata Editor can help you check and add metadata, and the Book Browser makes it easy to see your files — but you can always hand-edit content.opf in Code View if you need to tweak manifest ids or spine order.

Design-wise, keep text within safe margins (no type within 8–12% of the edge), use high-contrast colors and fewer than three typefaces, and avoid tiny decorative fonts for the title since they get lost at thumbnail size. If your cover is busy, add a subtle vignette or color overlay behind title text to increase legibility. Test the final EPUB in multiple readers (Calibre ebook viewer, Apple Books, Kobo, and a mobile reader) because each will render cover display slightly differently. Finally, remember that EPUB covers don’t need to include a back cover or spine the way print covers do — focus on a single, striking front image that tells the reader what kind of story or content they’re about. If you want, I can walk through a step-by-step Sigil workflow with screenshots next — would you like a compact checklist or a detailed walkthrough?