I don’t really trust anything to stay available on the web anymore.
A few months ago I moved all my bookmarks (you don’t want to know how many decades of bookmarks I have) to Anybox, a Mac and iOS bookmarking app. It’s tag-based, and has a lot of nice features, but one of the most useful is that I can tell it not just to bookmark something, but also to download it (in a variety of formats). So if I toss something in my “I should write about this” folder, I can be confident that when I finally get around to writing about it, I’ll still have a copy. Plus I can read things when I’m offline. And Anybox is all local, so I’m not depending on some cloud service other than iCloud for device syncing.
I’ve also started saving notes to it, since it supports notes, images, and files as well. I suspect that over time it may become my main repository “quick things I want to record for later”.
I might start using it instead of Mastodon bookmarking as well, although I do have a half-started project to write something that imports my Mastodon bookmarks to Obsidian. Generally if I bookmark something on Mastodon, I’d also like to include any links the post references as well.