If you no longer use the Opera Web browser, delete it from your system to free disk space on your Windows 8.1 computer or from your mobile device. You can select to keep or delete your user data -- bookmarks and Web browsing history, for example -- during the uninstall process on your computer. All user data is removed when you uninstall the Opera app from your mobile device.
Windows 8.1 Computer
Open the Control Panel in Windows 8.1 by pressing "Windows-X" to display the Power User menu and then selecting "Control Panel." Click the "Uninstall a program" link in the Programs section to view all programs installed on your PC. Select "Uninstall" to display the Opera Installer window. To delete all user data from the computer, check the "Delete my Opera user data" box. Click "Uninstall" to uninstall the software.
Android 4.4 and iOS 8
On an Android 4.4 device, tap the "All apps" icon from the Home screen to view all apps, hold on the "Opera" app until the "Uninstall" icon appears at the top of the screen and then drag the app over the icon to uninstall it.
On a iOS 8 device, open the Home screen, hold on the "Opera" icon until a small "X" icon appears in its upper left corner and then tap the "X" icon. Confirm your action to uninstall Opera.