FreeFileSync

FreeFileSync compares folders and synchronizes them — mirror, update, or two-way sync. Ideal for backing up to external drives, keeping work and home machines in sync, or moving large amounts of data. Handles network shares, detects moved and renamed files, and supports versioning. Cross-platform with a clean GUI. Free and open-source. One of those tools you install once and reach for every time you need to sync, backup, or compare folders.