The view through my canon 100D viewfinder is blurry [duplicate]

The title sums it up. I upgraded to full frame and when I reused my canon 100D I realized that I just could not see clearly through the viewfinder. Everything is blurry, even the parameters, even when the focus is clearly made on an object. The focus is clear however using live view.

I see well, on my 6D it is great but on the 100D it is very frustrating to just see everything blurry. Could it be something with the apparatus? (Else I suppose I will have to blame my eyes and the comfort of the bigger body’s viewfinder)

Thank you for your answers