Disable Auto-Completion for Fields in Salesforce Through Browser Settings

Your Salesforce settings do not control the autocomplete functionality, but this can be changed by customizing your browser settings.

To Disable Auto-Fill on your Internet Explorer Browser

1. Open Microsoft Internet Explorer. 
2. Click Tools and then Internet Options. 
3. In the Internet Options window click the Content tab. 
4. Click Settings under AutoComplete
5. Check or Uncheck the options you wish to or not to use AutoComplete. 
6. Click OK and OK again

To Disable Auto-Fill on your Mozilla Firefox Browser 

1. Open Mozilla Firefox. 
2. Click Tools then Options. 
3. Click Privacy & Security.
4. Under History, choose Firefox will: Use custom settings for history. 
5. Uncheck Remember search and form history. 

To Disable Auto-Fill on Google Chrome Browser

1. Open Google Chrome. 
2. Click the three lines beside star on the top right and select Settings.
3. Select the Autofill and passwords section and expand the area for which you wish to disable Autofill.
4. Toggle the setting to OFF.

To Disable Auto-Fill on Safari Browser 

1. Open your Safari browser.
2. Click Safari in the program menu and select Preferences in the drop-down menu.
3. Click on the Autofill tab in the Preferences window.
4. Click on each of the check boxes next to the autofill options to deselect them, turn off the autocomplete for each option.