1. Open a browser on your computer

2. Go to instagram, login

3. Right click on the page and select "inspect" (Or just press "F12")

4. (As shown in the picture below) Select the "Application" tab

5. Select "Cookies" at the left side

6. Find the "sessionid" value, copy

7. Return our page, paste the "sessionid" value, input the instagram post link. Click download

Your Cookie(sessionid) only stored in your device.