There is little doubt that a library is essential for genealogists. Still, with the emphasis on researching at a library, we may be forgetting about an essential part of its online presence, digital collections.
I realize not every library website includes digital collections, but enough do to include them when considering the public library located where your ancestors lived.
A digital collection is an online collection of digitized material that range from newspapers to historical photographs, books, and documents. While these collections aren't typically described as "genealogical," they have genealogical value. These collections will be found on the library website under a research or collections heading (for example). They may also be referred to as a digital archive or digital collection.
Let's look at an example from the Evansville, Indiana Public Library. While it's probably more apparent that a large public or academic library hosts digital collections, don't assume a local public library would not. In this example, their digital collections are found by clicking on the word Collections at the top toolbar, and then under Special Collections, choose Digital Archive.
"The Digital Archive collection created by the Evansville Vanderburgh Public Library contains images of photographs, postcards, cartoons, and documents representing people, places, and things in and around Evansville, Indiana.
Original images in this collection are from the Indiana Collection, located at Central Library in downtown Evansville, or from local residents."
So, what has genealogical value here? Almost everything, but pay special attention to the directories and yearbooks. Once you find the collection you're interested in, you can browse it to find the exact item like any digitized book collection you are familiar with. Once you select a singular directory, you can search within that book.
Once you're done exploring those, the homepage for the Digital Archive includes links to other collections, including genealogical.
Although I chose to start with a US example, any online library may include digital collections. Consider this example from the Medicine Hat, Alberta, Canada public library. In this case, the digital collections are part of a more extensive offering the library has, combining free and paid subscription databases. Not clearly labeled, this one took a little more effort to find, but it was under Books & More at the top toolbar and then All Online Resources.
Like most libraries, this one includes their subscription-based offerings, accessible with a library card, but they also have links to free collections, including the Alberta Heritage Digitization Project which is "free online access to cultural and heritage materials. Browse newspapers from 1885, read entire books about local communities, research legal documents, view historic photographs, and explore much more!" Yearbooks are just one of the genealogical finds you'll see in this collection.
Libraries are vital for genealogists but don't forget what they can offer your research virtually. An online search of your ancestor's local public library (or even another one nearby) might reveal historical photographs, newspapers, directories, or digitized books that can help your genealogical search. Don't stop at the library homepage or even the catalog. Explore the entire website to see what genealogical items might exist.