Which method involves a single step for users to subscribe to an email list?

The method that involves a single step for users to subscribe to an email list is Single Opt-In. This process allows users to join an email list simply by providing their email address, which is then immediately added to the list without requiring any further action or confirmation from the user.

This straightforward approach is beneficial for maximizing the number of subscribers, as it minimizes friction in the signup process. Users appreciate the ease of signing up without needing to verify their email address, making it a preferred method for many marketers who seek to grow their audience quickly.

In contrast, other methods, like Double Opt-In and Confirmed Opt-In, require a two-step process where the user must first submit their email address and then confirm their subscription by clicking a link sent to their email. This reduces the likelihood of spam sign-ups but introduces an extra step that may deter some users. Mandatory Opt-In, while emphasizing necessity, may not directly apply as a widely recognized standard in the same way as the others mentioned. Thus, Single Opt-In stands out as the most straightforward and user-friendly method.