What formats for newbie?

[Paredon]

My question has probably been asked 10,000 times, so maybe someone can point me to a thread where it's discussed.

I'm about to publish a digital book (epub) that I want to sell via my website, and I would like to know what formats I should make it available in. I created it with Sigil on a Mac, so I assume it's all ready for Mac users - or do I have to tweak it for Apple?

I also assume the #1 choice is Kindle, so I'll start looking for software to convert it to Kindle.

Are Kindle and Apple enough, or are there additional formats I should consider?

Thanks.

[DNSB]

Amazon/Kindle and ePub (everybody else) are the two major formats.

For Kindle formatting, you can send Amazon an epub and they will convert it for you. See Kindle Direct Publishing for more information. For do it yourself, you can use calibre to convert your epub to mobi (for antique Kindles), AZW3 and with the help of the KFX Output plugin to KFX. For quick testing, you can use Kindle Previewer on your computer though it is not as useful as it once was.

One recommendation is to test your epub and Kindle content on multiple apps and devices. For my uses, I use a couple of versions of ADE and Thorium on my Windows PC, Kobo, Pocketbook and Kindle apps on my iPhone/iPad plus physical Kobo and Kindle ereaders.

I don't bother with worrying about Android apps since they tend to be very cavalier in their treatment of my carefully crafted CSS and—generally—their epub3 support is pathetic.

[Quoth]

Upload of epub to Amazon KDP is actually only converted for their customers (and they decide what format to give customer). The only 100% way to know what Amazon is doing with an epub is to buy it by Download and Whispernet on at least two kinds of Kindle.

I upload epub to Smashwords/D2D (free) so I don't have to have a Mac. Smashwords distribute to Apple Books, Kobo, Barnes & Noble and others.
Amazon KDP (free) and Google Playstore Play Books (free) also get the exact same epub. Don't sign up to KU on Amazon as then you can't publish anywhere else, not even free on your own web site.
I upload also a dual mobi to Smashwords for their direct Kindle users as unlike Amazon they don't know what kindle model someone has.
I test any new kind of format/ layout on
Epub:
Kobo Sage and Libra (I don't bother testing kepub format)
5″ Sony PRS350
4.7″ P47L €80 approx ereader
Android from Version 4.x (Aldiko Basic) to 11.x (Lithium, Pocketbook) from 4.3″ screen to 10″ screen.
I don't test Apple Books because if the epubs are OK it should be OK as it's basically epub (Kindle for Apple is a different kettle of fish! Used to be like "old mobi") Also my iPhone 6 isn't supported by Apple store, unlike 4.1 Android on Playstore (at least resently)!
I don't bother testing on Google PlayBooks Android ereader now.

Kindle:
PW3 (azw3)
K3 (old mobi and azw3)

If in doubt and there is new format/layout stuff not used before I'll buy the published Amazon book (epub upload) in old Mobi (download to PC for DXG), azw3 (Download to PC for PW3) and KFX (Direct WiFi Whispernet for PW3). I had an Oasis (v 2) but gave it away. Not needed.

If you dowbload the "preview" from Amazon KDP it's simply the epub you uploaded and you are supposed to use Send to Kindle or Amazon Preview program (neither of those is trustworthy!).
I found Kindle Preview useless.

[Quoth]

I check that all internal links work and images are suitably scaled on small screens, large screens, 150 dpi and 300 dpi. Also that fallback fonts "work".

Only reflowable. Fixed layout are not proper ebooks and Fixed Layout epub3 is only to pretend to publish as an ebook and other than that it's a less compatible alternate to PDFs. Fixed layout epub3 or PDFs won't work on phones or typical ereaders. Over half of ebooks are read on phones.

Text books usually need tablets. Fiction will even work on a 1.5″ (160 x 160) screen (badly). A 3.5″ 4:3 1/4 VGA (320 x240 ) is the absolute minimum, but rare now.

[Paredon]

Wow, lots of details to wade through. Thanks for all the tips.