The second release candidates for the 1.66.0 release are now available at: <https://dl.bintray.com/boostorg/prerelease/> The in progress release notes are: <http://www.boost.org/users/history/in_progress.html> Library documentation is available at: <http://www.boost.org/doc/libs/1_66_0/> The SHA256 checksums are as follows: 596389389c005814ecb2a6b64c31dccd2c3e6fbc5a802b4dfada999ae5844628 boost_1_66_0_rc2.7z 5721818253e6a0989583192f96782c4a98eb6204965316df9f5ad75819225ca9 boost_1_66_0_rc2.tar.bz2 bd0df411efd9a585e5a2212275f8762079fed8842264954675a4fddc46cfcf60 boost_1_66_0_rc2.tar.gz e1c55ebb00886c1a96528e4024be98a38b815115f62ecfe878fcf587ba715aad boost_1_66_0_rc2.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy.