I want to upload YT hack vids

How do I delete all firefox data, cookies etc before logging each account?
Clear the browser like its the first time I opened it

Use mozilla profiles thay store cookies and cache in diferrent folders

Cookies can be useful because it keeps track of items that save your personal information including login credentials-so sites can remember you and what your preferences are.While you visit your site every time it automatically saves your information.
However, cookies can act as a privacy risk due to the amount of information they can hold. Cookies record your personally identifiable information so they can help auto-fill forms on browsers. This information may include your name, address, account login credentials, and more. If you want to delete cookies you will lose the convenience of stored passwords and other data.