The OED Online subscription is often expensive for individuals. Archive.org provides a legal way to access the older, out-of-copyright volumes for free.
The OED is famous for its historical approach. Every entry includes chronologically arranged quotations—from sources like medieval manuscripts to modern tweets—to illustrate how words have lived. Because the full physical set can span twenty or more volumes, a digital PDF version is often the only practical way for individuals to house the collection. Finding the OED on Archive.org
While the OED is currently available as a high-tech subscription-based website, the archived PDF versions offer unique benefits:
The foundational work led by James Murray. It is the most common version found on Archive.org.