What type of backup includes only the data that has changed since the last backup?

An incremental backup is designed to include only the data that has changed since the last backup of any type, whether that was a full backup or another incremental backup. This method is efficient in terms of storage and time because it avoids duplicating data that has not been altered, making the backup process faster and consuming less space on the storage medium.

When a full backup is made initially, all data is copied. With subsequent incremental backups, only the files that have changed since the last backup (regardless of type) are included. This means that if there are multiple incremental backups following the full backup, you would need the last full backup and all subsequent incremental backups to restore the system to its latest state.

In contrast, a differential backup includes all changes made since the last full backup, which can lead to larger backup sizes over time compared to incremental backups. A mirror backup creates an exact copy of the current state of the data, replicating the files and folders as they are at that moment, rather than focusing on what has changed. Therefore, the only type of backup that captures only the data that has changed since the last backup is the incremental backup.