Primo is a "discovery tool;" it produces integrated search results across Washington University Libraries’ Classic Catalog, most of the academic journal databases, and some of the newspapers and eBooks. It cannot search within the text of books WUSTL Libraries only owns in print, nor does it search most of our primary source databases. 

Google Books searches the full text of books and magazines that Google has scanned, converted to text using optical character recognition (OCR), and stored in its digital database. As of October 2019, Google celebrated 15 years of Google Books and provided the number of scanned books as more than 40 million titles. Google allows four levels of access: full view (books not under copyright can be read in full online and downloaded); preview: (a percentage of the book can be read online); snippet (2-3) lines of text surrounding the queried search term – is displayed in can be read), and No preview (these books have not been scanned, so only the metadata such as the title, author, publisher, number of pages, ISBN, subject and copyright information, and in some cases, a table of contents and book summary is available.

Google Scholar - the world's largest single index of academic journal articles. A study has estimated GS contains approximately 100 million articles, or 79–90% of all academic articles published in English. 

WUSTL Library Classic Catalog searches the Washington University Libraries’ collections of books, journals, newspapers, conference proceedings, government documents, microforms, video, and audio recordings. The Classic Catalog searches Washington University Medical School’s Becker Library collection as well. Searching the catalog will tell you if we own a particular journal and in which database the digitized issues are held, but you cannot use the catalog to search within issues of the journal. It will, however, lead you to the digitized collection.

MOBIUS is an 80-member consortium including 64 academic libraries,11 public libraries, 4 special libraries, and the Missouri State Library located primarily in Missouri but also include libraries in Oklahoma, Iowa, Kansas and Texas. Their combined catalog has over 29 million items, and a courier service delivers library materials to member libraries once per day, 5 days per week.

WorldCat is a meta-catalog which searches for materials held by tens of thousands of institutions (mostly libraries) worldwide. It contains over 540 million bibliographic records in 483 languages. Many items in WorldCat can be borrowed through Interlibrary loan (ILL).