iOS - Safari
1. Open the "Settings" App, and navigate to the "Apps" section.
2. Find and select "Safari."
3. Tap the "Clear History and Website Data" button.

See also: https://support.apple.com/en-us/105082
Android - Google Chrome
1. Open "Chrome."
2. On the right of the Search Bar, Tap the Kebab Button ( ⁝ ) to display an Action Menu.
3. Tap the "Delete browsing data" Button.
See also: https://support.google.com/accounts/answer/32050?hl=en&co=GENIE.Platform%3DAndroid