When you exit the Snapchat app, you are not necessarily logged out. If you don't want your account to stay open, you must sign out before closing Snapchat.
Steps
Method 1 of 3: Sign out of the app

Step 1. Open Snapchat
Tap the white ghost icon on a yellow background.

Step 2. Open your profile
Swipe down on the camera screen to go to your profile page.

Step 3. Press ⚙️
The icon is located at the top right of the screen.

Step 4. Log out
Swipe down and select Sign Out at the very bottom of the page.

Step 5. Tap Sign Out
The Snapchat login page should appear.
Method 2 of 3: Sign out of the account management site

Step 1. Open the account management page
This site allows you to manage parameters of your Snapchat account such as downloading your Snapcode, purchasing Geofilters, changing your password, etc.
When you log out of this site, you do not log out of the application on your mobile device

Step 2. Click ☰
The icon can be found at the very top right of the page titled Manage my account.

Step 3. Select Sign Out
The option is at the top of the page. You will be logged out of the account management site.
Method 3 of 3: Delete your Snapchat account

Step 1. Open the app
Tap the white ghost icon on a yellow background.
- If you're not signed in, tap To log in and enter your username (or email address) and password.

Step 2. Open your profile
Swipe down on the camera screen. You will be taken to your profile page.

Step 3. Select ⚙️
You will find the icon at the top right of the screen.

Step 4. Tap Support
The option is towards the bottom of the page in the section More information.

Step 5. Select My Account & Settings
The option is at the bottom of the screen.

Step 6. Tap Account Information
You will find the option at the top of the section My account and settings.

Step 7. Select Remove My Account

Step 8. Open the link
Tap the link page in blue in the first sentence of the second paragraph which begins with "Go to this page".

Step 9. Enter your password
Type it in the corresponding field in the middle of the screen.
You may also need to enter your username in the corresponding field

Step 10. Tap Continue
Your account will be deactivated for 30 days. At the end of this period, it will be permanently deleted.
If you want to reactivate your account before the 30 day deadline expires, just log into Snapchat
Advice
- Lock your device screen to keep your Snaps private.
- If you see a message informing you that your Snapchat account has been blocked, you can unblock it from the account management page.