To improve security and privacy, and to comply with a Federal government mandate, NCBI is moving all of its Web sites and services, including Web APIs, to HTTPS only by September 30, 2016, which was subsequently extended to November 9. At that point, HTTP traffic for GET and HEAD requests will be redirected. All other requests will be rejected. This change will provide users with greatly increased privacy and security on the NCBI site. To prepare for this change, NCBI ran a series of tests, which are now completed.