Google and Samsung have been pushing the RCS standard a lot over the past few years, and it seems to have worked. Even Apple has announced that it will bring support for RCS Universal Profile to iPhones next year. Ahead of that release, Google is adding even more features to Google Messages RCS.
Google has quietly added support to send and receive Ultra HDR format images through RCS via the Google Messages app. This feature was spotted by TheSpAndroid (via Android Authority) through the application code for Google Messages. While the publication wasn't able to test the feature by itself as it lacks a device that supports Ultra HDR, it asked some Pixel 8 users. Apparently, those users confirmed that they can send Ultra HDR format images through Google Messages and RCS.
The latest version of the Google Messages app features a code string that says bugle.support_ultra_hdr. The Ultra HDR feature was introduced with Android 14, but not all devices running that operating system version support it. For example, Samsung phones running Android 14-based One UI 6.0 don't support the Ultra HDR format. However, we expect Samsung to bring support for this image format in the next version of One UI.
Ultra HDR format adds HDR (High Dynamic Range) metadata to standard JPEG files. This is smart, as devices that don't have screens that support HDR images can continue to show standard JPEG data without the HDR information. However, if apps do not support Ultra HDR, they will remove HDR metadata and display an SDR image despite the device supporting Ultra HDR. So, it will take some time for all important apps to bring Ultra HDR support.