Here is a list of some cool CSS page transitions.
3D Cube Page Transition
Dev: Hubert Warzycha
Reveal content animation (and menu)
Dev: Tobias Glaus
React Animated Page Transitions
Dev: Sarah Drasner
Fullscreen Layout Page Transitions
Dev: Marcelo Ribeiro
CSS Page Transitions
Dev: brandonjp
Squish transition
Dev: Adam Wagner
Responsive bodymovin modal / page transition
Dev: Jonas Sandstedt
Simple CSS3 Page Transition
Dev: Paul DeCotiis
Material design transition
Dev: David Marland
Page transition CSS3
Dev: TOMAZKI
GSAP Cubic bezier page transition
Dev: Maciej Siwanowicz
Page transition / Preloader
Dev: spes
Page Transition with Loader
Dev: John Heiner
Page Transitions
Dev: Mergim Ujkani
Expanding card page transition effect
Dev: Rachel Smith
Simple Page Transition
Dev: ktsn
Vue2 page transitions with GSAP
Dev: Tim Rijkse
Article transition page
Dev: Muna
Tiles Page Transition (CSS)
Dev: Milan Ricoul
Simple Page Reveal Effect
Dev: Jamie Hunt
Page reveal CSS only
Dev: Dejan90
Dummy Multi Layer Page Reveal Effect
Dev: Mehmet Burak Erman
Page Reveal Effect
Dev: Kevin Levron
Just another CSS UI
Dev: Jamie Coulter
Transform: translate
Dev: Cassandra Rossall