@DDG thanks for the question on shoe widths, and for the request to add these details to our website pages. Typically, the shoes on our website will be designated as narrow or wide, however if neither of those are specifically noted, the shoe should be considered to be available in a medium width only. For men, medium width = D, wide = E. For women, narrow = A, medium = B, wide = C-D. That said, there are brands that run wide (ex: Lowa) or run narrow (ex: La Sportiva), and this would certainly be a helpful place to see specific measurements (as you suggest); in the meantime, here in the community, we can definitely help if you have questions on how certain brands run! Finally, as you shop on REI.com, on the left rail you have the option to narrow your search to include only brands/models that are available in a wide width.
Thanks again for the suggestion!