Mobile

Step 1: From the home screen, go to Settings > Safari.

Step 2: Toward the bottom of Safari's settings screen, tap the button for Clear History and Website Data, then tap Clear History and Data to confirm.

Desktop

Open settings — Click Safari in the upper-left corner of the main menu bar and select the Preferences option near the top of the drop-down menu. Then click the Advanced tab located in the top navigation bar and check the box directly on the bottom that says Show Develop Menu in Menu Bar. Doing so will add a new menu to Safari by default.

Clear the browser cache — Click the Develop menu near the middle of the main Safari menu bar and select the Empty Caches option.