Safari does not provide an option to auto-delete cookies on quit as other browsers do. So the idea is, to delete the cookies on shut down of Mac OS X using a shell script:

1. Create an empty Cookie file

• Open Safari
• Go to Preferences –> Security - > Show Cookies
• Delete all Cookies
• Quit Safari without loading any website in between
• Open Finder
• Go to „/Users/XXXXXX/Library/Cookies/“ (Replace XXXXX with your username)
• Copy „Cookies.plist“ to „CleanedCookies.plist“ in this folder*

Done! Now you should see two files in the folder „~/Library/Cookies/“: „Cookies.plist“ and „CleanedCookies.plist“!

2. Create autostart shell script

• Open Terminal

• Type: „cd /Library/StartupItems/“

• Type: „sudo mkdir /DeleteCookies“ - > Enter your password

• Type: „sudo pico“ (a shell text editor will open)

• Paste this inside:*

  #!/bin/sh 
  
  . /etc/rc.common 
  
  #StartService () 
  #{ 
  #} 
  
  StopService () 
  { 
  cp -f /Users/XXXXX/Library/Cookies/CleanedCookies.plist /Users/XXXXX/Library/Cookies/Cookies.plist 
  } 
  
  RestartService () 
  { 
  StopService 
  } 
  
  RunService "$1" 
  
  

• Change „XXXXX“ to your username (at two places!)

• Press „Ctrl - X“ (it asks if it should save the document)

• Press „Y“ (it asks for a file name)

• Type „DeleteCookies“

• Don’t close the Terminal! We will need it again.*

3. Create StartupParameters

• In Terminal type: „sudo pico“

• Paste this inside (with { and }):*

  {quote} { Description = "DeleteCookies"; Provides = ("Deletes Safari cookies on shut down"); Uses = ("Disks"); } {quote}

• Press „Ctrl - X“ (it asks if it should save the document)

• Press „Y“ (it asks for a file name)

• Type „StartupParameters.plist“

• Now you may close the Terminal*

Now you should see two files in the folder „/Library/StartupItems/DeleteCookies/“: „DeleteCookies“ and „StartupParameters.plist“. Done!

4. Restart the system

• Restart your computer
• After reboot it will tell you that StartupItems do not have the right permissions
• Click on „Correct Permissions“ (2 times for the two created files)
• Restart your computer again.*

Now your Safari-Cookies should be deleted automatically each time when you shut down your PC.

Text source: apple community

Use something like Firefox Focus.