Inline forms beat popup forms

A button that says "Sign up" requires two steps: click the button, then fill the form. An inline form visible on the page requires one step: fill the form. One fewer step, consistently higher conversion.

The popup introduces doubt. "What will happen when I click this?" The user doesn't know if they'll see a form, a pricing page, or something else. That uncertainty, even if it lasts half a second, is enough to stop some people from clicking.

An inline form with an email field and a submit button communicates everything instantly. The user can see what's required before making any commitment. The cognitive cost is lower because there's no mystery about what comes next.

The exception is when the form is long. A 7-field form inline on the page looks intimidating. In that case, a button that opens a form in a clean modal can work better because it separates the decision to start from the work of completing. But for simple email captures, inline wins.