What is the Cover check?
Cover check is the button under the preview. It reviews your cover the way a shopper's screen will, and lists what it finds. The button carries a count when there is something to look at.
Nothing it says blocks an export. It is advice, and some of it you will want to overrule.
The four thumbnail panels
Almost nobody first sees your cover at full size. They see it in a search result on a phone. The panel renders your cover four ways:
- Search result — about 160 pixels tall, roughly a phone results page.
- Also-bought — about 100 pixels, the recommendation strips.
- Grayscale — the same 160 pixels with the color removed. This shows value contrast, which is what survives when color doesn't, and it is also close to how the cover prints in black and white.
- Squint — detail thrown away and blurred back in. If you can still tell what kind of book it is here, the composition is doing its job.
Most cover problems are visible in these four and invisible at full size.
What it checks
Type
- Three or more typefaces. Two is the working limit; a third reads as indecision rather than range. Give one face two jobs at different sizes instead.
- The title isn't much bigger than everything else. A cover reads as amateur when the author name competes with the title. Aim for the title at two to three times the name — until the name is the thing selling the book.
- The author name is missing from the front. The name is set on the book and prints on the spine, but nothing on the front carries it. Often an oversight; sometimes deliberate.
- Very small title type, which will vanish at thumbnail size.
Color and composition
-
The title has too little brightness separation from the art behind it. Below about 28% apart, the letters stop separating once the cover shrinks — and they go first in grayscale and in print. The finding names the measured figure.
The fix that works is the title's own brightness: taking it to near-white or near-black usually clears 60%. A halo tidies letter edges but cannot manufacture separation between two colors of similar brightness — if the color has to stay, move the title to a calmer part of the cover instead.
-
The title sits on the busiest part of the artwork. This is a different fault from low contrast: a title can have plenty of brightness separation and still be unreadable because the art behind it is churning. The finding tells you how much noisier that band is than the calmest band of the same height, and how far down the calm one starts.
Print and content
- Spine too narrow for text. Under about a quarter inch there is no room to set a title without it touching the folds, and KDP will not print spine text on a book that thin at all. It is left off.
- Publisher logo under 300 DPI at the size it actually prints. A logo is line art blown up to print size — the one upload where a small file shows immediately.
- No blurb on the back cover. It's the second thing a browsing reader looks at, and a blank back reads as unfinished even when the front is strong.
- A blurb under 9 pt, which is uncomfortable to read on paper at arm's length. Most trade paperbacks sit between 9 and 11.
- Both dust-jacket flaps empty, on a jacketed hardcover.
The count can be one behind
The number on the button comes from the quick checks only. The contrast and composition readings need the fully composed cover, which is too much work to redo on every frame, so the panel can legitimately show one or two findings more than the badge. Open it to see everything.