How to Securely Wipe a Hard Drive or SSD Before Selling It

Deleting a file, then emptying the recycle bin, doesn't erase the data — it just removes the pointer that tells the operating system where to find it. The actual bytes sit on the drive until something else happens to overwrite that physical space, which on a drive you're about to hand to a stranger might be never. Anyone with basic recovery software, the same kind covered in our guide to recovering deleted files, can often pull those files right back.

Why Hard Drives and SSDs Need Different Approaches

Traditional spinning hard drives (HDDs) store data in a way where overwriting the same physical location with new data genuinely destroys the old data — a single full-disk overwrite is generally considered sufficient by modern standards, contrary to the old myth that you need seven or more passes.

Solid-state drives (SSDs) are different. Because of wear-leveling, the drive's controller spreads writes across cells to extend the drive's lifespan, which means a "delete and overwrite" tool run from within the operating system may not actually touch the physical cells holding your old data — the controller might have already moved that data elsewhere. For SSDs, the reliable method is the drive's built-in Secure Erase or Sanitize command, which works at the firmware level and resets every cell directly, rather than relying on the operating system to guess which physical locations to overwrite.

Step-by-Step: Windows PCs

1. Back up anything you want to keep first — this process is irreversible by design.
2. Open Settings → System → Recovery, and choose "Reset this PC."
3. Select "Remove everything," then choose the "Clean the drive fully" option when offered (sometimes labeled as a more thorough option that takes longer). This performs a full overwrite, not just a fast reset.
4. For an SSD, check whether your drive manufacturer provides a dedicated Secure Erase utility (most major SSD brands do) — this is more reliable than the operating system's built-in reset for SSD hardware specifically.

Step-by-Step: Mac

1. Back up what you need, then sign out of iCloud and any other accounts on the machine.
2. On Apple Silicon Macs, use Erase All Content and Settings from System Settings, which securely erases the built-in storage and reinstalls macOS — this is the recommended path and effectively replaces older manual disk-erasing steps.
3. On older Intel Macs, boot into Recovery Mode, open Disk Utility, erase the drive, then reinstall macOS from Recovery before handing the machine over.

Phones and Tablets

Modern iPhones and Android devices encrypt all stored data by default. Because of this, a factory reset that discards the encryption key makes the remaining data on disk unreadable, even though it technically isn't overwritten — the key is what mattered, and it's gone. Before resetting, remove the device from your account (sign out of iCloud/Find My, or remove the Google account) so the next owner isn't locked out by activation lock, and confirm the reset completed before handing the device over.

Physical Destruction: When It's the Right Call

For a drive that held highly sensitive data, or one that's failing and can't complete a software wipe reliably, physical destruction is the surer option — drilling through the platters of an HDD, or through the memory chips of an SSD, in several places. Many electronics recyclers and some office supply stores offer certified drive destruction as a service if you'd rather not do it yourself. The U.S. National Institute of Standards and Technology publishes formal guidance on this exact decision — matching the sanitization method to how sensitive the data was — in NIST Special Publication 800-88.

Once the wipe is confirmed, physically remove any drive-specific paperwork or labels, and if you're recycling rather than selling, most municipalities and manufacturers offer e-waste drop-off programs that keep the hardware out of a landfill.

External Drives and Old Backup Disks

The same considerations apply to external hard drives and old backup disks sitting in a drawer, which people tend to overlook because they're not part of the "main computer" being sold. An external drive that once held a full backup, then got replaced by a newer one and forgotten, is still a complete copy of everything it held at that point — years-old tax documents, photos, browser-saved passwords exported at some point, whatever was on the source machine at the time. Before selling, donating, or discarding any external drive, run the same wipe process described above rather than assuming an old, unused drive is somehow lower risk than the one currently in your laptop.

Verifying the Wipe Actually Worked

For extra confidence on a drive that held especially sensitive information, connect it to another machine afterward and check whether it appears as genuinely empty — no partitions with recognizable data, no folder structure from the old operating system. Recovery software (the same category covered in our guide to recovering deleted files) can also be run against a wiped drive as a check: if it can't find recoverable files after a proper wipe, that's a reasonable practical confirmation that the process worked as intended, even without specialized forensic tools.