Deleting something from a website or app does not necessarily mean every copy has disappeared.
People can take screenshots, download files, save messages, quote posts or repost content somewhere else. Search engines, archives and other systems may also retain information for periods of time.
This does not mean that everything online is permanent forever. It means you should avoid treating deletion as a guarantee that nobody else will retain or remember something.
Think about the long-term effect of information before sharing it. This is particularly important for personal information, private conversations, photographs, location details and content that could affect someone else's safety or reputation.
If something has already been shared, focus on what you can control: remove content where possible, ask for harmful reposts to be removed, secure affected accounts and seek help if the situation involves serious harassment, threats or exposure of private information.