As genealogists, we have become accustomed to having online digitized genealogy record websites, some of which have massive collections of digitized documents such as the big four: Ancestry.com, MyHeritage.com, FamilySearch.org, and Findmypast.com. There are, of course, hundreds of other websites with significant digitized content online also. However, we often ignore or miss the really large, online collections of books and records that aren't labeled as "genealogy" websites. The most important of these is the Internet Archive or Archive.org.
Since its beginnings in 1996, the Internet Archive or Archive.org, has become an online repository for millions of genealogically valuable books and other records in many different languages. As of the date of this post, the Archive.org has 36,149,861 eBooks and texts. Along with its collections of internet webpages, videos, audio files, software files, and images, Archive.org may now be the largest library ever assembled. The Library of Congress reportedly has 32 million catalogued books and about 61 million manuscripts. See https://www.loc.gov/about/general-information/ The total number of items in the Library of Congress is about 173 million. The total of all the online digital files on the Internet Archive is about 771,060,300,000 items. Yes, that is billions of items. Additionally, the entire collection of items on the Internet Archive are fully searchable whereas, the Library of Congress' holdings are nearly all still on paper. A search on Archive.org for the term "genealogy" just in the books section of the website, returns 612,941 items and that is just the items that have the word genealogy specifically.
Searching on the website can be interesting. You have to choose between searching for metadata (cataloging entries) and text. I generally do only a text search. But the key to using the website is that the entire collection is searchable by Google so you just add the URL "archive.org" to your search on Google and it will return all the instances of your search term from the website. In this way, you can search for an individual person, county, country, or whatever.
Learning about the Internet Archive is like waking up and finding out that you have been living next to a large, unexplored country and didn't realize it was there all the time.
If a book or whatever happens to be copyright protected, you need to remember that the Internet Archive is a library and you can still check out the book sometimes for only an hour, but you have to register with a free registration first.
You might want to explore more than just the books. You might also want to always mention the Internet Archive when you list the major online genealogy websites.