Where do my replays appear after I share them?
Like friendly challenges, replay sharing will be visible in the alliance chat. You will be unable to share your replay if you are not currently in an alliance.
 
Why can I not share replays right after I’ve updated the game?
After every update, older attack and defense logs can be missing certain information, like new or updated units and buildings, which is preventing them from being shared. You can read more about this in the Attack/Defense logs are missing information article.
 
Why is there not a share button for my world war replay?
This is because world war replays are already visible (if enabled) to members of your alliance and the alliance you’re battling!