Microsoft is now testing Windows 10 build 17649 internally. The new Windows 10 Redstone 5 build 17649 (10.0.17649.1000 rs_prerelease.180412-1450) was compiled on April 12, 2018.
Windows 10 Redstone 5 preview build 17643 is now available for Skip ahead Insiders. The latest build comes with improvements for Sets, Microsoft Edge, Data Sense, and Magnifier. Windows Insiders who are also Office Insiders can try out Sets with Office. In addition, Microsoft WebDriver is now a Feature on Demand.
The ISO files for Windows 10 build 17643 are now available for download. You can download it from the link below.