If you have a compatible device*, you can view HDR images by expanding the image to its full size. Otherwise, you'll only get the (still gorgeous) SDR version. Any image that has HDR data will be tagged with "HDR" and will have the [HDR] prefix in its title.

*What is a compatible device? Your device MUST support HDR (obviously), and you must be visiting Newgrounds in a Chromium-based browser (such as Google Chrome, Microsoft Edge, or the Brave Browser). Furthermore, "Ultra HDR" images are currently known by me to be supported on these devices:

• Microsoft Windows 10 and above
• Samsung Galaxy S24 and above
• Google Pixel 8 and above (possibly also Pixel 7 series)
• Apple iPhone 14 and above

This is not an exhaustive list, and support is still growing. You can test for yourself whether you can view HDR image by visiting this website and viewing the test images: https://gregbenzphotography.com/hdr/

Keep in mind that HDR may be a very drastic, or a very subtle effect. Bright images with intense lighting will gain more from HDR viewing than dim images with dark lighting, even if they're still "HDR".