Preparing a photo here does not turn on WhatsApp HD. They are separate steps: create a useful image file, then choose the appropriate option in the chat composer. Our HD preset fits a photo inside a 4096×4096 pixel box, preserves its proportions, and uses a 3 MB export cap. Those numbers describe this tool's settings, not a promise about the size WhatsApp delivers.
WhatsApp's HD help page explains the chat quality control and the default setting under Storage and data, then Media upload quality. Check the selection when sending, especially if you share a prepared file through another app's share sheet. The setting belongs to WhatsApp, not this compressor.
An HD photo message is still different from handing someone your untouched original. If a client needs a master file for editing, keep that original and consider the Document attachment workflow. If a friend simply needs a clearer view of a scene or face in a chat, the photo workflow may be more convenient. Choose based on what the recipient needs to do with the image, rather than assuming one label means every pixel is preserved.