No, I don't want to install your bullshit app [0]. Stop wasting the real-estate at the top of my screen.
And at the bottom of the screen, they often have another floating bar, asking if I'm ok with cookies. (Of course, the website loads just fine without me having clicked 'Ok', so either they're asking permission for something that does nothing, or they're asking permission only after having done it.)
javascript:(function()%7B(function%20()%20%7Bvar%20i%2C%20elements%20%3D%20document.querySelectorAll('body%20*')%3Bfor%20(i%20%3D%200%3B%20i%20%3C%20elements.length%3B%20i%2B%2B)%20%7Bif%20(getComputedStyle(elements%5Bi%5D).position%20%3D%3D%3D%20'fixed')%20%7Belements%5Bi%5D.parentNode.removeChild(elements%5Bi%5D)%3B%7D%7D%7D)()%7D)()I've used it to selectively edit content out of forums on occasion.
1) Reader mode (which I use extensively)
2) Unobstruct [0] does not meet your "without installing", but does a great job nonetheless
[0] - https://medium.com/@tgaul/introducing-unobstruct-230e4e95cf5...
https://alisdair.mcdiarmid.org/kill-sticky-headers/
Or Reader modes in Safari, Firefox, as mentioned.
Edit: found one solution: https://outline.com/SV3V7N