Should one or more of these libraries be marked as "deprecated" in their corresponding meta/libraries.json? Array Assign Chrono Compatibility compressed_pair enable_if ForEach functional mem_fn move MPL Ratio ResultOf Typeof The new website could use this information to annotate the library. We could add a "reason" field to libraries.json which is displayed on the site. The website could have a checkbox, "hide deprecated", enabled by default. We could show the reason for the deprecation. For example, that mp11 is a more modern and functional version of MPL. Or that ForEach is now a C++ language feature. The authors and maintainers of those libraries would need to opt-in to this, although we could have someone work up pull requests for some or all of those libraries. There might be more libraries that belong on the list, feel free to add. Another idea we might consider is to add a preprocessor deprecation warning, unless the user opts-in by defining BOOST_ALLOW_DEPRECATED or something. Before we do that though, we should ensure that no non-deprecated Boost libraries are using the above libraries. Thanks