Important Note: Kindle devices (and possibly apps on ios/android/windows) targeted for non-English speaking countries might have a different set of default fonts. I've seen reports starting in 2016 (here and here) that (unspecified) versions of Kindles devices for India include by default the Indic Noto Sans font. This font claims to support 583 languages as of this writing. If you know of other non-European fonts which are included onby default on your device or app, feel free to mention in the comments)
Kindle 4 (aka Kindle Touch)
Kindle Fire (version unspecified)
(This info comes from a great Roger Packer article, How to Choose typography for ebooks). PS, would be nice to know which of these would be the system defaults for serif and sans).
Fire HD 8
- Bookerly
- Caecilia
- Georgia
- Palatino
- Baskerville
- Helvetica (Sans Serif)
- Helvetica Light (Sans Serif)
- Lucida
(Info Source: This video review of Fire HD 2016).
Kindle Paperwhite
- Caecilia
- Caecilia Condensed
- Baskerville
- Futura
- Helvetica (Sans Serif)
- Palatino
- Bookerly (only for 3rd generation and after)
- Publisher Font
(This info comes from this article about 1st gen Paperwhite and this article about Bookerly).
Kindle Basic 7 (7th generation, 2014)
- Baskerville
- Bookerly
- Caecilia
- Caecilia Condensed
- Baskerville
- Futura
- Helvetica (Sans Serif)
- Palatino
- Open Dyslexic
Kindle Basic 8 (8th generation, 2016)
- Amazon Ember (Sans Serif, see this comparison video)
- Baskerville
- Bookerly
- Caecilia
- Caecilia Condensed
- Baskerville
- Futura
- Helvetica (Sans Serif)
- Palatino
- Open Dyslexic
Kindle Oasis
- Amazon Ember (Sans Serif, see this comparison video)
- Amazon Ember Bold
- Baskerville
- Bookerly
- Open Dyslexic
- Palatino
- Publisher Font