Note, you are shown this "onboarding-page" a second time after your initial installation of xIFr, because there's a Firefox bug that might have closed this page the first time, just as you where about to read it.
Congratulations!
xIFr version has been installed.
With this tool you can see a lot of the metadata that can be embedded in JPEG files. Various data of types EXIF, IPTC and XMP are supported.
To see (if there are) any recognized metadata in an image, you can usually just right-click the image and choose "View EXIF data" in your browser's contextmenu. But to get the best of xIFr, I suggest you to read the introduction:
Also, make sure to make a visit to xIFr's Options Page where you can
adjust some aspects of how xIFr looks and behaves. Look for the wheel
in the metadata-popup to access the options.
My personal favorite settings are "Dark Theme" and the "Snap right" popup positioning.
I hope you'll find xIFr useful and enjoy using it...
/Stig