Incremental backups are the best solution because they only back up data that has changed since the last backup of any type was performed, thus saving storage space while keeping the backup up to date. Differential backups, while similar, back up all the data that has changed since the last full backup, which can lead over time to greater storage use than with incremental backups. Synthetic backups and mirrors are not types of backups that specifically focus on changed files between backups in comparison to the last backup or full backup.