Microsoft is now testing Windows 10 build 17121 internally. The new Windows 10 Spring Update build 17121 (10.0.17121.1 rs_prerelease.180310-1319) was compiled on March 10, 2018. This build might roll out to insiders next week. Recently, build 17120 was also compiled.
Windows 10 Spring Update preview build 17115 is now available for Insiders. The new insider preview build includes new privacy settings with a new design to help customers make focused choices about their privacy and offers two new settings for Inking & Typing and Find my device.
The ISO files for Windows 10 build 17115 are also now available for download. You can download it from the link below.