Official manufacturer overview
Seagate Expansion portable — official family overview
Seagate Technology · Expansion portable family overview. This listing is STNN4000400 4TB with the specified USB-C cable; capacities, enclosure thickness, connections and regional services vary across the range.
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Seagate Expansion portable • STNN4000400
More room for the files that travel with you.
Keep a larger photo library, project folders and everyday documents together on a portable 4TB hard drive. The Seagate Expansion STNN4000400 connects to a computer through its supplied USB Micro-B to USB-C cable, with a rounded enclosure that travels easily between a desk and a bag.

Room for your own library
Carry the bigger collection.
4TB of decimal storage gives files a dedicated home outside the computer. Use it for media, documents and an additional copy of work you want to keep. Available space is lower after formatting and system functions, and the capacity reported by an operating system may use a different measurement.
The connection, explained
USB-C at the computer. Micro-B at the drive.
The included 0.5m cable connects the drive’s USB 3.0 Micro-B socket to a compatible USB-C computer port. A computer with USB-A can use a suitable USB 3.0 Micro-B-to-USB-A cable, sold separately. USB 3.0 has a 5Gbps interface signalling rate; file-copy results depend on the hard drive, host, file sizes and operating conditions.
Windows and Mac
Move files across platforms with exFAT.
The drive comes formatted as exFAT for file access on supported Windows and macOS systems. Keep exFAT when sharing ordinary files between both platforms. Time Machine and Windows File History have different format requirements: choose the appropriate native file system for that backup workflow. Reformatting erases existing files, so copy anything you need elsewhere first.
Choose your backup routine
A separate copy is a useful starting point.
Drag and drop files for straightforward storage, or use compatible Seagate Toolkit software to set up a backup plan on Windows. Toolkit also offers mirror folders on Windows and Mac. Mirroring follows edits and deletions between folders; it is different from keeping independent historical copies. Software functions depend on the supported operating system.
A considered portable form
A rounded enclosure for a larger capacity.
This 4TB model measures 117.8 × 85 × 20.9mm and weighs 246g. The official ordering specification lists the finish as black. Its white status light indicates readiness and activity; use the operating system’s safe-removal procedure before unplugging the cable.
Package and support
The cable and the next steps are included.
The box contains the Expansion portable hard drive, its 0.5m Micro-B-to-USB-C cable and a quick-start guide. Seagate lists a two-year limited warranty for these EMEA models, subject to regional terms and serial-number validation. Rescue Data Recovery Services are listed for the range, with availability and entitlement varying by country and supplied unit; confirm eligibility through Seagate rather than assuming a recovery outcome.

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