As a sample, O'Brien attached the post with a red foliage image encoded at 97% quality using Google's JPEG encoder guetzli. Click on the image of the tweet post to enlarge it (you may still be zoomed out), but you'll be able to see the quality of the image better. However, all EXIF information will be deleted when uploaded.
Starting today, Twitter will preserve JPEGs as they are encoded for upload on Twitter for Web. (Caveat, cannot have EXIF orientation)
— Nolan O'Brien (@NolanOBrien) December 11, 2019
This may allow photographers to review the importance of Twitter. The thumbnail and preview display will be transcoded as before.
There are some opinions that the video quality of Twitter will deteriorate significantly, so next time you should consider improving the video quality.