If you’re about to sell or give away a computer, it’s important to ensure that all of your personal data is erased first. This is a pretty simple task when it comes to traditional spinning hard drives, and there are plenty of tools to make sure the drive is completely and securely wiped. Solid State Drives, however, are a different story. SSDs use something called “wear leveling,” which ensures that no one cell gets written to too many times. This is to keep the drive from wearing out, but it also means that it isn’t possible to write over (or erase) every part of the drive. For most people, simply going through the process of erasing and reinstalling the operating system will be sufficient. This will erase the known file system, but it still would be possible to recover data if someone was motivated enough. If you want attempt to take it a step further, a program called Darik’s Boot & Nuke (DBAN.org) is a good option.
The absolute best way to keep your data secure on an SSD is to enable drive encryption before you start using it. The good news is that mobile devices like phones and tablets encrypt by default. The only exception to that would be in the case of SD cards on Android phones, so make sure to turn on encryption for that as well. On desktop computers, there are built-in features that will encrypt the drive. On Windows, you’ll be looking for BitLocker, and on the Mac you’ll want to enable FileVault. By doing this, even if the drive is erased, the data won’t be recoverable without the password to decrypt it.