Facebook Messenger has announced that it has taken the resolution of the photos sent to recipients. If you did not know, messaging applications such as Facebook Messenger, Telegram, and Wattsapp apply a kind of quality compression before photos reach the person to whom they are sent.
Here are some comparisons that show the difference
The Facebook Messenger resolution has been "2K" for a while - or 2048 x 2048 pixels. A new update will allow you to send files up to 4096 x 4096 pixels. Many phones these days use 12MP cameras, the largest of which is between 4000 and 4048 pixels. So if you send files from an iPhone X, Pixel 2, or Samsung Galaxy S8 or Note8, your receiver should get them in full quality. Facebook also mentioned that photos will be sent "as soon as before", so there should be a new kind of file size reduction.
The feature with the highest resolution images (Facebook calls "4K images") are now circulating on iPhone and Android for users in the US, Canada, France, Australia, the United Kingdom, Singapore, Hong Kong, Japan, and South Korea . Facebook will continue to release 4K images in other countries "in the coming weeks".