The release candidates for the 1.66.0 beta release are now available at: https://dl.bintray.com/boostorg/beta/1.66.0.beta.1/source/ The SHA256 checksums are as follows: 0e137e61069e95f61fe0e46aa4a5432e65e209e87d470ea3c15b0ea1327583ac boost_1_66_0_b1_rc1.7z eff4854c1a672830c55fd2323ebe42d5d83e0f7a3d0a9d354d8bf55289831fa0 boost_1_66_0_b1_rc1.tar.bz2 f4fb07aa1ec639707570e42a848796d9a8155f23d1ece0f0a6a0cbee99807038 boost_1_66_0_b1_rc1.tar.gz d5f480441223f45427199697edbdd78145499084f835597247a452d2a7e1e798 boost_1_66_0_b1_rc1.zip The in progress release notes are at: http://www.boost.org/users/history/in_progress.html And the documentation is at: http://www.boost.org/doc/libs/1_66_0_beta1/ 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.