{
  "slug": "differential-backup",
  "term": "Differential backup",
  "aliases": [],
  "definition": "A differential backup captures changes accumulated since its designated full-backup base, rather than only changes since the preceding differential backup.",
  "note": "In SQL Server, changed extents are tracked against the differential base; COPY_ONLY full backups do not reset that base. [sql-differential] Terminology varies: SNIA's differential incremental backup instead refers to changes since the latest full or incremental backup, so it is not used here as an alias. [snia-differential]",
  "status": "shipping",
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-14",
  "advantages": [
    {
      "text": "SQL Server restores the matching base and selected differential without earlier differentials.",
      "citationIds": [
        "sql-differential"
      ]
    }
  ],
  "limitations": [
    {
      "text": "The matching differential base must be retained; the newest full backup is not necessarily that base.",
      "citationIds": [
        "sql-differential"
      ]
    }
  ],
  "related": [
    "full-backup",
    "incremental-backup",
    "backup",
    "point-in-time-recovery",
    "restore-test"
  ],
  "citations": [
    {
      "id": "sql-differential",
      "title": "Microsoft SQL Server: Differential backups and differential bases",
      "url": "https://learn.microsoft.com/en-us/sql/relational-databases/backup-restore/differential-backups-sql-server?view=sql-server-ver17",
      "accessed": "2026-10-14"
    },
    {
      "id": "snia-differential",
      "title": "SNIA Dictionary: differential incremental backup",
      "url": "https://www.snia.org/education/online-dictionary/term/differential-incremental-backup",
      "accessed": "2026-10-14"
    },
    {
      "id": "hesela-backup-evidence",
      "title": "Hesela: Backup verification is not a restore test",
      "url": "https://hesela.com/analyses/backup-verification-is-not-a-restore-test/",
      "accessed": "2026-10-14"
    }
  ]
}