Free publishing tool
Book cover technical score and thumbnail test
Upload a cover to measure pixel dimensions, aspect ratio, luminance range, and small-size visual variation before publishing.
Use the book cover technical score and thumbnail test
Upload a cover to check pixel dimensions, aspect ratio, luminance range, and small-size visual variation.
This bounded check cannot see your title as text or judge genre fit, focal clarity, originality, rights, or reader taste. Use the linked human thumbnail test too.
Quick answerA technical book-cover score can flag dimensions, aspect ratio, luminance range, and loss of visual variation at thumbnail size. It cannot decide whether a cover is original, accurately signals the genre, owns the artwork rights, or will appeal to readers.
What does the thumbnail test reveal?
Retailers display covers much smaller than production size. At that scale, weak title separation, crowded detail, low contrast, and an unclear focal point become obvious. Use the score as a fast technical screen, then compare the actual thumbnail beside current books aimed at the same readers.
What does an automated cover score miss?
The browser cannot reliably read the title hierarchy as designed, understand symbolism, verify originality, assess market positioning, or inspect licensing. It also cannot know whether intentional restraint is appropriate for a literary cover or whether a maximal composition is expected for a specific subgenre.
How should you improve a weak result?
Increase the separation between title and artwork, simplify competing detail, strengthen the main focal point, and export at the platform's requested resolution. Recheck after each meaningful change. Preserve the editable design so the thumbnail, ebook file, and print wrap remain one coherent system.
Frequently asked questions
What does the cover score measure?
It checks pixel dimensions, aspect ratio, luminance range, and small-size visual variation.
Does the score judge market appeal?
No. Genre fit, originality, title hierarchy, rights, and reader taste still need human review.
Is the uploaded cover stored?
No. The technical check runs in your browser.