Just about all of these devices have a built-in delete function, often called Factory Reset or Restore to Factory Defaults. Be careful: many of these devices also say you can reset the device by holding down a power or reset button for 10 seconds. Most of the time, that’s just a reboot or restart; it doesn’t delete your data. Make sure you’re using instructions to truly restore the device to a “fresh from the factory” clean state.

Additionally, to be thorough, it’s probably a good idea to sign yourself out of any online accounts and disconnect from wifi before resetting the device. Below we cover instructions 

Amazon Echo

• You can often reset a device from the device itself
• Then de-register the device using Amazon’s website
  • Visit amazon.com and sign in
  • Mouse over where it says “Hello [your name]”, and select Your Content & Devices
  • Click Devices in the Manage Your Content and Devices menu
  • Find your device in the list, and click the button with the ‘…’ to the left of the device name
  • Click Delete Voice Recordings, then confirm by clicking Delete
  • Click the ‘…’ button again, click Deregister, and then confirm by clicking the Deregister button.

Android Devices

• First forget any wireless networks, and sign out of your Google account(s)
• Encrypt your data: go to Settings > Security and find the Encrypt Phone section
  • If it says ‘Encrypted’, you’re already set.
  • If not, tap Encrypt Phone and follow the on-screen instructions
• Finally, go ahead and factory reset the device

Apple TV

• First, forget any wireless networks
  • Open Settings, then select Network > Wi-Fi
  • Select the wireless network (SSID) you wish to forget
  • Select Forget Network
  • Repeat the above for any other wireless networks, as needed
• Then reset the device.

PlayStation

(note instructions below are for PS3; steps for other versions may vary)

• Sign out of the Playstation Network
• Delete all users from Users > select user icon > press triangle > select Delete
• Disconnect wifi by resetting back to default settings
• Delete all saved data from Settings > System Settings > Restore PS3 System

Roku

Roku does not offer a way to disconnect from wireless; you can simply run factory reset

Xbox One

Sign out of your Xbox Live profile, then reset to factory defaults