Google Chrome

1. Type chrome://settings/clearBrowserData in the browser bar (where you usually enter a URL).

2. From the dropdown menu, select a time range to clear your entire cache/cookies.
   
   Then, check: 
   
   Browsing history
   Download history
   Cookies and other site and plug-in data
   Cached images and files
   
   

3. Click Clear browsing data.

4. Finally, close all your Chrome windows and re-open Chrome.

Firefox

1. In the browser navigation menu, select History > Clear Recent History.

2. From the dropdown menu select a desired time range or Everything to clear your history.
   
   
   In the Details panel, select:

   Browsing & Download History
   Cookies
   Cache

3. Click Clear now.

4. Finally, close all of your Firefox windows and re-open Firefox.

Internet Explorer

Optimizely only supports IE8 and higher.

1. Select Tools > Delete Browsing History (in older versions) or Safety > Delete Browsing History (in newer versions) from the browser's top-navigation menu or settings menu.

2. Deselect Preserve Favorites website data.
   
   
   Select:

   Temporary Internet files and website files
   Cookies and website data
   History

3. Click Delete.

4. Finally, close all of your IE windows and re-open IE.

Safari

For Desktop:

1. Select Safari > Clear History from the browser's top-navigation menu.

2. From the Clear menu, select your desired time range or all history to clear your browser cache and cookies.

3. Click Clear History, then close all of your Safari windows and re-open Safari.
   
   

For iOS:

1. Open the Settings app.

2. Tap Safari.

3. Tap Clear History and Website Data, then close all of your Safari windows and re-open Safari.

For Android:

1. From the Settings menu, tap Apps or Application Manager.

2. Choose the All tab.

3. Find your web browser, then tap it.

4. Tap Clear Data, then Clear Cache, then close all of your browser windows and re-open your browser.

Android encompasses a wide variety of devices and browsers, so these steps may differ for you.