Pretty yucky looking. Are you the homeowner? Have you tried any cleaning solutions yet?

Yes, im the homeowner

ive tried a razor and goo gone

I am not sure I would use a razor. It might damage the window finish. It is definitely yukky, and I sure wouldnt want to see it when looking out my windows. It does appear to be some type of glue, although, sure dont know why it would be there. wd 40 sometimes works on a lot of different things. No idea what that is, or if it might work, but, worth a try, I guess.

Warm soapy water and some cloths you don't care about throwing out. I would glove up too.

Looks like there is black mold/wood rot underneath it. I wonder if the windows leak and someone spread something trying to keep the water from coming in and now it's aged and turned brown?

Sometimes making a poultice to leave for a period helps to soften to make it easier to remove…. Try searching along those lines.