Popup modal dialogs are the most common type of modal. They tend to appear as a window over a portion of the page, often using a contrasting color or animation that attracts user attention. The background they appear against is usually darkened or blurred, disabling the main content. Most importantly, they force users to either take action within the popup or close it to continue engaging with the main content again.

These modal dialogs can appear in response to user-initiated actions, such as clicking a button or link, or they can be triggered automatically by the system in response to a specific event, such as an error or warning.