The Kindle mobile apps for iPhone or iPad and Android do not have a "Sign out" button. Instead, users must unregister their device. By doing so, it is unlinked from the Amazon account and you will no longer be able to make purchases through it or view the content that has been purchased with it. Once you have unregistered your device (the best equivalent of logging out) you can log into your account and register the device with a different account or with the same one. You can even unregister a device through your Amazon account, this feature will prevent others from accessing it if it is ever lost or stolen!
Steps
Method 1 of 3: Unregister the Kindle App for iPhone or iPad

Step 1. Open the Kindle app
You can do it in two ways:
- Browse through your application pages until you find the one for Kindle, which has the silhouette of a person reading in black on a blue background.
- From your home screen, swipe right to open the search function. Press the search bar, enter the word "Kindle" and click on the application when the menu below appears.

Step 2. Press the Menu icon
Find this icon (three vertical lines) in the upper left corner of your screen.
- If you are using an iPad, skip this step.
- If you have a book open, be it on an iPad or iPod, press the settings menu followed by "Library." This will return you to the main screen.

Step 3. Scroll down to the bottom of the menu and press “Settings”
If you are using an iPad, press the "Settings" icon. Find this icon (a white gear) at the bottom right corner of the screen

Step 4. Locate the “Register” section and press “Update”
This will take you to the page to unregister.

Step 5. Click on “Unregister Device”
"All downloaded content will be deleted from the device, do you want to continue?" If you register the device with the same account, all content will return to your library.

Step 6. Press “OK”
This will unregister the device with your account. The connection to the Amazon account you signed up with will have been deleted.

Step 7. Enter the Kindle application to register your device
- Press "Email or cell phone number" and enter the email or cell phone number that is associated with your Amazon account.
- Click on "Password" and enter your Amazon account.
- Press the "Login to my account" button. The device will automatically register with the Amazon account you signed in to.
Method 2 of 3: Unregister the Kindle for Android App

Step 1. Open the Kindle app

Step 2. Press the Menu button
You'll find this button (a thumbnail of the Kindle logo) in the upper left corner of the screen.
If you have a book open, press the settings menu followed by "Library." This will bring you back to the main screen

Step 3. Locate the section that says “My Account” and click on “Settings”

Step 4. Click on “Unregister this device”
This option is located in the registry section. Thus, you will exit the account. Your device's connection to the Amazon account you registered it with will have been removed.

Step 5. Log into your account in the Kindle app to register your device
- Open the Kindle app.
- Click on "Start reading."
- Enter the email or cell phone number that is associated with your Amazon account.
- Enter your Amazon account password.
- Press the "Enter" button. The device will automatically register with the Amazon account you entered.
Method 3 of 3: Unregister an Amazon Device Remotely

Step 1. Enter the Amazon website
Android users can register their devices through the Amazon Appstore application. When you download it and log into your account with it, the device will automatically register and appear in the “My devices” list. If it is lost or stolen, this feature will allow you to unregister your device with your Amazon account.
This app is only compatible with Android devices

Step 2. Login to your account
- Enter your email and your cell phone number.
- Then enter your password.
- Click on the "Login" button.

Step 3. Press “Hello, (insert name) my account”
Find this option to the right of "Gift Cards and Registration" and to the left of "Subscribe to Prime."

Step 4. Scroll down to the “Manage content and devices” section and click on “My Apps and Devices”

Step 5. Press "My Devices"
Find this option in the "Management" section of the left sidebar.

Step 6. Click on "Actions"

Step 7. Select “Unregister device”
You will have logged out of your account (the connection between your device and the Amazon account you registered with was actually removed).