HDR (High Dynamic Range) is the next advancement in photo and video viewing. In my opinion it's an even bigger advancement than 4K or other high-resolution improvements.
Unlike traditional "HDR" photography which is just designed to simulate HDR on a regular display true HDR can only be achieved with the right device and software.
If your device hardware and software support it you can get a much more realistic and vivid viewing experience from an HDR image than a traditional image. It cannot really be described, it's something you have to witness in person to truly experience.
Currently the best way to view HDR content is on Instagram in a Chrome browser on supported hardware. The Instagram smartphone app is second best. This will likely change in the future.
See here for ways to check if your device supports HDR viewing.
Details for Nerds
Essentially HDR is the ability for a display to show extremely bright portions and extremely dark portions at the same time. This leads to a much more vivid viewing experience.
However, proper support for HDR is still limited. Both the hardware and software used for viewing HDR needs to support specific formats like HDR10+ or DolbyVision
Hardware support for HDR is currently limited by can be found on the following devices, among some others (+ means "or newer"):
                                • iPhone 12 +
                                • Google Pixel 7 +
                                • MacBook Pro 2018 +
                                • MacBook Air 2018 +
                                • MacMini 2018 + (with compatible display)
                                • Various TVs and computer displays
Software support for HDR is also very limited. Sites such as Instagram and Threads have some basic support but most other sites currently do not. Instagram will display HDR content in the smart phone app and in the web browser, but only if the browser supports HDR viewing such as Google Chrome (Safari does not work).
Below I have put together a sample gallery that can be viewed in a support app on a supported device / display as per above.
I will start including selective HDR photos on Instagram and other platforms as they start supporting it.
A more detailed explanation of all this can be found here.
(View the gallery using a compatible display like on a 2018 or newer MacBook Pro and using Chrome, both of which are required to view HDR properly)
Additional Info
Example of traditional simulated HDR on a regular (SDR) display. Imagine the image on the right but the light from the sun is almost piercingly bright like it is in real life and the clouds lit up with light reflected from the sun. It's almost like being there, vs a traditional display, when you see it in person.
Here are some further examples of how HDR displays work conceptually. This first image describes how the brightness range of an HDR display is much greater than a traditional display and thus looks much more realistic and more natural.
The second image shows how the color and contrast are also improved with HDR displays.