Microsoft has released Windows 10 Insider Preview Build 17123 for PC to insiders in the fast ring. Microsoft continues to iron out bugs in Windows Mixed Reality. Microsoft has added the High Efficiency Image File Format (HEIF) image format to Windows 10. In order to test this new format, insiders also need to join the Windows App Preview Program for the Photos app, which now supports HEIF. In addition to traditional single images, HEIF supports encoding image sequences, image collections, auxiliary images like alpha or depth maps.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-insider-build-17123-supports-the-high-efficiency-image-file-format-heif/