What is the largest site that UpdraftPlus can back up?

UpdraftPlus’s architecture imposes no limits upon the size of backups. As long as your server has the disk space available to create a backup, and as long as your web hosting company does not apply any other artificial limits (e.g. does not give you enough outgoing bandwidth to allow your backups to reach their destination in the cloud), then UpdraftPlus can back up anything. It is known to be successfully backing up websites of up to 12 gigabytes (12,288 megabytes), and we’re not aware of any website that won’t back up because of being too big.