Should I select KDP or IngramSpark?

Choose the printer you're actually uploading to. Four are supported — Amazon KDP, IngramSpark, Lulu, and B&N Press — and each computes spine width, barcode placement, and wrap margins a little differently, so the Cover Maker tailors the export to whichever you pick.

• Publishing only on Amazon? Choose KDP.
• Using IngramSpark for wider distribution (bookstores, libraries)? Choose IngramSpark.
• Printing through Lulu or B&N Press? Choose those — their specs are not interchangeable with KDP's.
• Doing more than one? That's common — you can generate a correct wrap for each. See Can I create both KDP and IngramSpark covers?

One thing to check before you commit to a plan: not every printer offers every binding at every trim size. KDP makes no dust jackets at all, and Lulu doesn't print 5.25 × 8. The full grid is in Which printers and bindings can I make a cover for?

One cover purchase covers all of these variants, so choosing another later doesn't cost extra.