Rewrite DnD guides

[Josh-Cena]

• Fix Recommended drag types for DND API uses nonstandard type for dragging nodes. #35633
• Fix Include full list of possible Drag Types #28969
• Fix Drag & Drop topic should be 3 separate topics #27654

Notable changes:

• Non-standard features removed or explicitly noted as non-standard
• Substantial information is removed from the landing page; the landing page only contains concepts
• "Drag operations" page rewritten to only cover event firing and handling
• "Recommended drag types" page merged into a bigger page about drag data store
• New "Kanban board" guide to demonstrate in-page DnD, to parallel file DnD.

I did not fix #27654 the way requested, because DnD in fact does not contain three distinct topics. "In-page DnD" very much uses the same features as dragging in or dragging out, it just happens that there are certain events that don't fire for dragging in or dragging out.

[github-actions]

Preview URLs (19 pages)

• /en-US/docs/Web/API/DataTransfer/addElement
• /en-US/docs/Web/API/DataTransfer/clearData
• /en-US/docs/Web/API/DataTransfer/dropEffect
• /en-US/docs/Web/API/DataTransfer/effectAllowed
• /en-US/docs/Web/API/DataTransfer/files
• /en-US/docs/Web/API/DataTransfer/getData
• /en-US/docs/Web/API/DataTransfer/items
• /en-US/docs/Web/API/DataTransfer/setData
• /en-US/docs/Web/API/DataTransfer/setDragImage
• /en-US/docs/Web/API/DataTransfer/types
• /en-US/docs/Web/API/DataTransferItem/kind
• /en-US/docs/Web/API/DataTransfer
• /en-US/docs/Web/API/DragEvent
• /en-US/docs/Web/API/HTML_Drag_and_Drop_API/Drag_data_store
• /en-US/docs/Web/API/HTML_Drag_and_Drop_API/Drag_operations
• /en-US/docs/Web/API/HTML_Drag_and_Drop_API/File_drag_and_drop
• /en-US/docs/Web/API/HTML_Drag_and_Drop_API/Kanban_board
• /en-US/docs/Web/API/HTML_Drag_and_Drop_API
• /en-US/docs/Web/CSS/:-moz-drag-over

External URLs (3)

URL: /en-US/docs/Web/API/HTML_Drag_and_Drop_API/Drag_data_store
Title: Working with the drag data store

• https://ryanseddon.com/html5/gmail-dragout/ (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Web/API/HTML_Drag_and_Drop_API/Kanban_board
Title: Kanban board with drag and drop

• https://docs.github.com/en/issues/planning-and-tracking-with-projects/learning-about-projects/about-projects (1 time) (Note! This may be a new URL 👀)
• https://trello.com/ (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2025-10-02 00:06:18)

[wbamberg]

I am finally looking at this PR.

[wbamberg]

This is great. I've long been sad about the DnD docs on MDN but never managed to do it, as this PR shows, it's a lot of work.

I thought this was a really excellent explanation though and great examples, it's a massive improvement.

[Josh-Cena]

I have bit the bullet and updated the drag data store page to describe exactly what browsers do, which may make it either messier or clearer, I don't know :)

[wbamberg]

👍 thanks. Great work!