Top 5 digital libraries of world

Universal Digital Library - Collection of millions of books, maps, manuscripts in multilingual format.

Project Gutenberg - More than 30,000 ebooks to read along with several audio books, CDs and DVDs.

Bartleby - An immense collection of reference, fiction, nonfiction books etcs

ibiblio - From offering ebooks to academic papers to music and streaming radio, it offers almost everything.

Google Books - More than 100,000 books and a fully searchable database.

Reference | https://www.jagranjosh.com/news/ndli-and-top-digital-libraries-of-world-146293