The increasing of image quality to HD results in more data consuming by the app and a bit more noticeable time to upload but shared photo will be in the HD Quality. This feature has started rolling out on all platforms including web across the world and Meta also looks forward to introduce a similar feature for sharing HD Videos that will be out soon.
Additionally for users who want to send standard quality photo will still have an option to select the upload quality of the photo. The current max HD resolution supported by WhatsApp is 4000 x 3000.
