You do not have to create an account, just select an existing account from one of the supported service providers. Only the bare minimum information is retrieved and saved in order to identify your account.
By signing in, all your expressions will be automatically saved to your account, where you have ability to organize and manage them. You can add titles and tags to organize your entries, as well as favorite any expressions.
You also get a valuable feature set with regards to your data privacy, where you are given the ability to restrict who can view and edit the information you save. If you want to permanently remove the saved data, you can easily do so from here. The delete link will be automatically tied to your account, so you never have to worry about losing it.
By signing in you also get the ability to enhance your skills and participate in the regex quiz along with thousands of other regex connoisseurs!