[rescbr]

At least JPEG contains downscaled thumbnails embedded into it as part of the EXIF stream. There's no need for the receiving device to rescale it again.

Pretty sure these newer formats do the same.

[kllrnohj]

That thumbnail is for grid-size, it's generally 50kb or less in size which ends up being around 300x240 or up to 500x500 on newer codecs.

It'll be visibly low-res and blurry until the full size decodes for full screen. Hence why I said "when tapping on a thumbnail"

[rescbr]

Oh, I missed the “tapping on” part.