Here is a summary of how to reset Amazon Echo to the state at the time of shipment.
It is rarely needed to use it normally, but in my case, I used it to cut a certain hardware failure.
I think it can be used when selling old echo.
If you have an Echo without a screen, you can reset it in the following operations.
In summary, it is OK if you try the bold method for recent models.
Once you press the action button for 6 seconds, you will once enter the "setup mode", but it is still a trick to keep the announcement "reset the device" until the announcement flows.
In the case of Echo with a screen, you can reset the state at the time of the factory by the following operation.(Echo Show, Echo Spot, Echo Show 5)
The "Settings" screen can be swiped the screen and opened from the gear mark icon.
Actually, you can reset even if you press and hold down the volume down button at the same time (20 seconds), but if you try both, the reset from the screen seems to be more powerful, so I recommend that.
It is interesting that it is not always necessary, but after these reset work, you may be required to reset your Amazon account or enter Wi-Fi password.
If you have forgotten, remember in advance.
Regarding this area, it seems that the Alexa app is considered to be easier to reset the Echo if it is linked to the Amazon account, so if you transfer it to another person, just in case, the Alexa app coordinated with Echo devices.It is a good idea to release it.
