There are a lot of valid answers to this! One is to use your platform's provided one, like OneDrive or iCloud. Another is to integrate with some other sync plat

There are a lot of valid answers to this! One is to use your platform's provided one, like OneDrive or iCloud. Another is to integrate with some other sync platform. Dropbox is a popular target for this. Peer-to-peer is another, although that obviously also come with limitations. Finally, bring-your-own-sync is a popular choice amongst open-source apps, where you provide a self-hostable sync server.