Backblaze, an online backup service, faced significant criticism for excluding cloud storage contents from its backups. This change was due to the complex nature of how services like iCloud Drive, Dropbox, Google Drive, and OneDrive handle files. These services often use modern APIs that make files appear locally when they are not fully downloaded. Users see placeholder files with cloud icons, requiring manual download.Maestral, a Dropbox client, operates differently by syncing a local folder with a Dropbox account. This means Maestral's Dropbox folder is a standard, regular folder. Therefore, Backblaze can successfully back up folders managed by Maestral because they are treated as regular local files. Services utilizing Apple's File Provider APIs, including iCloud Drive, present "magic folders" whose behavior is not well-documented.Interestingly, Dropbox's own Mac client still offers an older mode that bypasses the File Provider APIs. Reports indicate that Backblaze may or may not back up Dropbox folders in this mode, contributing to the overall confusion. The situation highlights the intricate and often undocumented technical challenges involved. The author expresses a desire to avoid these complexities. Using Maestral has allowed them to do so. They anticipate needing to address the issue if Maestral ceases to function. A linked post from Rob Halliday on the TidBITS-Talk forum is referenced as a starting point for deeper information.