I just saw another post regarding bookmarks on iOS where an Apple engineer made the following statement: [quote='855165022, DTS Engineer, /thread/797469?answerId=855165022#855165022'] macOS is better at enforcing the right behavior, so code that works there will generally work on iOS. [/quote] So I went back to my macOS code to double-check. Sure enough, the following statement: let bookmark = try url.bookmarkData(options: .withSecurityScope) fails 100% of the time. I had seen earlier statements from other DTS Engineers recommending that any use of a URL be bracketed by start/stopAccessingSecurityScopedResource. And that makes a lot of sense. If start returns true, then call stop. But if start returns false, then it isn't needed, so don't call stop. No harm, no foul. But what's confusing is this other, directly-related API where a security-scoped bookmark cannot be created under any circumstances because of the URL itself, some specific way the URL was initially created, and/or manipulated?