How to use it
- Upload the JPEG you want to inspect. It is read, never changed.
- Read the report: each marker shows as present or absent.
- Compare a file before and after uploading it somewhere to see exactly what that service removed.
What it looks like on an HDR screen
Simulated. On the screen you are reading this on, both halves are identical — an ordinary display has no extra brightness to give. This is how the difference reads on an HDR display.
What the converter actually builds
Both images above are real output from this converter, not an illustration. White areas of the gain map are the ones an HDR screen brightens; black areas stay exactly as they were.
Frequently asked questions
What does it check?
The MPF multi-picture segment, XMP gain map metadata, ISO 21496-1 metadata, how many images are embedded in the file, the dimensions and any ICC profile.
Why would HDR data disappear from my photo?
Most upload pipelines re-encode images for size and format consistency. A re-encoder that does not understand gain maps writes out a plain single-image JPEG, and everything else is discarded silently.
Does it detect Apple's HDR photos?
It reports Apple's gain map signatures when they are present, though Apple's scheme differs from Google's Ultra HDR and the two are not interchangeable.
Is my file kept?
No. It is read to produce the report and deleted afterwards.