Online backup with the Backup API

The SQLite Online Backup API copies the contents of one database into another while the source is running, replacing the historical approach of taking a shared lock on the database file, copying it with an external tool such as the unix cp utility, and releasing the lock — a method that works well in many scenarios and is usually very fast but has documented shortcomings. The pattern is three calls: sqlite3_backup_init() creates an sqlite3_backup object to copy data between two databases, from a file into an in-memory database or vice-versa; sqlite3_backup_step() copies pages, and a parameter of -1 copies the entire source database to the destination; sqlite3_backup_finish() releases the object, with errors read via sqlite3_errcode() on the destination connection. For progress reporting, sqlite3_backup_remaining() and sqlite3_backup_pagecount() return the pages left to copy and the total pages, as stored by the previous step call. Step in small batches on busy databases so concurrent readers are not held off (Koskamo editorial guidance). Scope: SQLite. Reviewed October 4, 2026.