A self-publishing platform's cover image requirements are usually specific and strict — particular pixel dimensions, a minimum resolution, and often a maximum file size, all while the cover needs to look genuinely sharp and professional, since it is one of the biggest factors in whether a browsing reader clicks on the book at all.
Steps
- Check your specific platform's exact requirements — dimensions, minimum resolution, accepted formats, and any size limit.
- Design or finalise your cover at the required dimensions, or resize an existing design to match.
- Compress with the Image Compressor at a light setting, prioritising quality given how important the visual result is here.
- Check the final file against every stated requirement before uploading.
Why cover image quality deserves extra care
Unlike many everyday compression tasks where a slight quality trade-off is barely noticeable, a book cover is genuinely a sales asset — it needs to look crisp both as a small thumbnail in search results and, often, as a larger preview image on the book's own page. Reserve the lightest compression setting that meets any stated size limit, rather than defaulting to a stronger setting for a smaller file than necessary.
Meeting both a minimum resolution and a maximum file size
Many self-publishing platforms specify both a minimum pixel resolution (to ensure the cover looks sharp when enlarged for certain print or preview purposes) and a maximum file size. These can pull in different directions — a large, high-resolution image tends toward a larger file, while a hard size cap pushes toward more compression. Start with a light compression setting at the full required resolution, and only increase compression strength if the file size genuinely exceeds the limit at that resolution.
Checking text legibility on the cover specifically
If your cover includes a title, author name, or other text, check that text remains crisp and fully legible after compression, both at full size and at the small thumbnail size the cover will often actually be browsed at. Text is one of the first things to show visible softening under compression, and a cover with blurry title text looks unprofessional regardless of how good the rest of the artwork is.
Preparing separate versions for different uses
- The main platform upload, meeting that specific platform's exact requirements.
- A version for your own website or social media promotion, which may have different, often more relaxed size requirements.
- A print-ready version, if you are also producing a physical edition, which needs considerably higher resolution than either digital version, following the general guidance in our guide to resizing images for print versus screen.
What to do if the platform rejects your cover for an unclear reason
If a cover is rejected without a clear explanation, systematically check it against every stated requirement one at a time — exact pixel dimensions, colour mode (some platforms specifically require RGB rather than CMYK), file format, and file size — since a rejection is often caused by one specific mismatch rather than a general quality issue with the image itself.
Keeping your source design file for future editions
Keep your original, layered design file (if you designed the cover yourself or worked with a designer) safely archived, separate from the final compressed export used for upload. This means any future edition, a series with a matching style, or a size requirement change from the platform can be addressed by re-exporting from the original design rather than trying to work backward from an already-compressed cover.
Meeting the platform's specific requirements
Different self-publishing platforms specify their own minimum resolution and maximum file size for cover uploads, and these requirements can differ meaningfully between platforms if you're publishing to more than one. Check the specific platform's current requirements before compressing, rather than assuming a size that worked for one will automatically be accepted by another, since a rejected upload due to an unmet minimum resolution requirement is a frustrating discovery late in the publishing process.
Keeping a full-quality master alongside the compressed upload version
Keep your original, uncompressed cover design file saved separately from whatever compressed version you actually upload to a given platform. If you later need a print-quality version, a higher-resolution export for a different platform, or simply need to make an edit to the cover, working from the original master avoids the quality loss of repeatedly re-compressing an already-compressed file.
Previewing the cover at actual size before finalising
Beyond meeting the platform's technical requirements, preview the compressed cover at roughly the size it'll actually display at — a small thumbnail in a search results list, for instance — since design details that look fine at full size can become illegible or lose impact once shown much smaller.
Frequently asked questions
What resolution does a self-publishing platform typically require?
This varies by platform; check your specific platform's current stated requirements rather than assuming a general figure applies.
Should I prioritise minimum file size or maximum quality?
Maximum quality within whatever the platform's limits allow, since the cover is a significant factor in a reader's decision to click on your book.
Does compression affect how the cover looks on an e-reader screen specifically?
A well-compressed image at appropriate resolution should look sharp on any standard e-reader or device screen; check the result at a size similar to how it will actually be displayed.
Can I use the same cover file for print and digital editions?
Generally not directly; print requires considerably higher resolution than digital, so prepare separate versions for each.
What if my cover has both photographic elements and text?
Use a moderate compression setting and check both the photographic detail and the text legibility specifically, since they can respond differently to the same compression level.
Is there a standard format most platforms accept?
JPG is commonly accepted and often required; check your specific platform's stated format requirements.
Is the tool free and private?
Yes. No sign-up, no watermark, and files are removed from the server automatically about an hour after processing.