Popup Maker

Popup Maker is an open-source WordPress plugin (since 2014) for building popups and forms to grow email lists. Conditional display logic shows forms only on specific pages, after a visitor has scrolled, following a time delay, or only to new visitors. It integrates with 12+ email services including Mailchimp, ConvertKit, ActiveCampaign, and others, and includes analytics to track impressions, conversions, and submission rates.

Teams on tight budgets will appreciate the free model and full control over form behavior. It requires more setup than premium builders but offers strong flexibility for custom display logic, and the open-source approach means no vendor lock-in when switching email services.