Modal Window (Wikipedia)
Wikipedia’s article on the modal window as a UI component — a separate article from “Mode (user interface),” focused specifically on the blocking-dialog case rather than modes in general.
License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/
Key points
- A modal window disables interaction with its parent window while staying visible; the user must resolve it to return to the parent. Contrasted with a modeless window (e.g. a palette window), which the user can freely switch focus away from.
- Four named use cases: drawing attention to vital information (though habituation undercuts this), blocking flow until required information is supplied (a password prompt, a file dialog), centralizing configuration into one place, and warning about an irreversible action (though usability critique favors undo over a blocking warning here too).
- Designer Alan Cooper’s defense of modals — restricting freedom protects users from a distraction they’d otherwise regret — set against the article’s own preferred alternative: a self-contained, single-task interaction that signals required fields visually (an asterisk, a red border) instead of blocking access to the rest of the interface.
- Problems: focus-stealing (a modal can intercept keystrokes or clicks meant for a different window or application entirely — a real privacy/security risk, not just friction, especially on a virtual desktop large enough that the modal isn’t even visible on screen); mode errors from a user not registering the modal demands attention; habituation from repeated exposure; and several operational restrictions (can’t move/minimize the modal or use cut/copy/paste while it’s open, sometimes obscuring the very information it’s asking for).
- Design recommendations: position a modal near whatever triggered it rather than centering it arbitrarily; use a semi-transparent dark background sparingly; make the dimmed background itself a close target (standard on mobile); follow each platform’s own button-placement convention (Windows: affirmative action lower-right; macOS: sheets with right-aligned commands).
- Modeless infobars are offered as an increasingly preferred alternative to a blocking dialog — a passive banner the user can absorb on their own schedule rather than one that interrupts.
- macOS Sheets: a panel that slides out from a window’s own title bar. It behaves like a mode within that one window (always on top, not in the window list, must be dismissed to keep using that window) but, critically, leaves the rest of the application — including any other open windows — fully usable. A mode scoped to one window rather than the whole application.