spec 2 linked patterns checked
MDN: Window beforeunload event
Documents the beforeunload event for warning users about impending unsaved data loss, including browser restrictions, sticky activation, mobile reliability limits, and the recommendation to attach listeners only while unsaved changes exist.
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What this source can teach
Use this source to check a technical or accessibility requirement against its exact wording and scope.
- Start with the original. Open the source and find the guidance or example relevant to your task.
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Pattern Decisions This Source Supports
| Pattern | Supported decision | Required contract | Claim note |
|---|---|---|---|
| Exit warning | Choose exit warning when departure has already been attempted and leaving would lose work or context that is not safely recoverable. | The warning appears only after a departure attempt or immediately before a known session boundary that could cause loss. | MDN documents beforeunload for preventing unsaved data loss and recommends conditional use. |
| Unsaved changes prompt | Choose unsaved changes prompt when a user action inside the product would abandon or replace dirty local edits before they are saved. | Opening the prompt never clears the dirty values. | MDN documents warning users about unsaved data loss and limiting listeners to actual unsaved-change conditions. |
Comparisons supported by this source
- Exit warning vs autosave form vs draft state vs confirmation dialog
MDN documents beforeunload as a browser event for warning about unsaved data loss and recommends conditional listeners.
- Unsaved changes prompt vs exit warning vs autosave form vs confirmation dialog
MDN documents unsaved data loss warnings and conditional use of browser leave protection.
Evidence Role
This source is treated as spec evidence. Its value comes from the specific claims and setting described above.
Publisher: Mozilla. Last checked: .