Vkontakte cover, why is the quality falling?

Question

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Hello!
Tried to make a cover.
Created in canvas, everything is fine; I load VK, the picture becomes dim, the colors are not bright, the quality is reduced. In the canvas itself, the image is perfect.
Created a cover in Photoshop, the same rigmarole.
Tell me what am I doing wrong?
Thank you!

Answer 1

This VK reduces the quality and there is no way to fix it on your part