What are the most common modifier keys for dragging objects with a mouse?

Question

What would you consider to be the most agreed upon modifiers and conventions, when dragging/dropping objects? For example, holding Ctrl while dragging could add a "+" to the cursor and cause a copy (instead of a move) operation on Windows.

(Single aspect are discussed here: Cancelling drag-n-drop action before drop, https://apple.stackexchange.com/a/83774/15596)

Answer 1

Here's a list of some common ones (including the one you listed)

1. Ctrl + Drag — Copy file
2. Shift + Drag — Move file ("in situations where copy is the default—like when you're dragging a file between two different drives")
3. Alt + Drag — Create shortcut for file
4. Right-Click + Drag — Will show a menu of options upon release

Most of these are related to dragging files, but the operations should be similar for most other drag-and-drop operations. It really depends on what you're dragging.

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EDIT: As some people have mentioned, those conventions are specific to Windows and not other operating systems. Here are the Mac equivelants of the above shortcuts:

1. Option + Drag — Copy file
2. Command + Drag — Move file ("in situations where copy is the default—like when you're dragging a file between two different drives")
3. Command + Option + Drag — Create alias for file
4. I couldn't find a universal equivalent to the Right Click + Drag that is found in Windows.

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Also, the other answers are saying that this area of UX is not a well-defined standard. Although I definitely agree that this is the case, it should be noted that there are many commonly used conventions that vary based on the content that is being dragged. For example, on Windows many 3rd party file managers mimic the shortcuts used in the default Windows Explorer. Also, Apple has a page in their Human Interface Guidelines which discusses drag and drop, which may help if you're developing for OSX. The conventions vary heavily however, whether you're dragging files, dragging images, dragging objects in a game level editor, etc. So you should analyze apps that use drag-and-drop in your context to see if there are any common patterns that you should follow.

Sources: Lifehacker [1, 2], Apple Support [1, 2], Ask Different

Answer 2

There are not strong standards of drag&drop use since it's not that popular and widely used.
Add to that fact that modifiers are basically hidden, so users will find them just by mistake or intentional search.

Test: Ask 10 random non-tech-savvy users about this. If you are lucky you will only get "Esc" as a consistent answer.

Depending on the programs each user use most, they will be more likely to know some of them but there are not universal ones (shared among all types of apps) modifiers for drag and drop.
Again 'Esc' possible being the only exception.

You might only find some conventions in similar type of applications e.g. Image Editing Software (Shift, Ctrl, Alt,etc to modify selection or other options depending on the tool you're using). So if you have to choose, look if there's any convention on similar software that the one you are designing.

Answer 3

1) I completely agree with Rewobs that it is a "poorly defined" "liltle used" "no common standards" area in UX.

2) Regarding "copy" specifically, I'm pretty sure the "only somewhat commonly accepted one" is, just as you say, option-drag means "copy, rather than just move".

(*) Note however that we immediately seem to be in disagreement, because on a Mac it is option-drag (to copy), whereas you report it is ctrl-drag (to copy) on Windows (I can't remember; and don't have a W machine at hand) - !

3) I observe that the 3D / game / modelling field is one field that heavily, indeed essentially, uses keyboard modifiers with mouse/dragging operations.

Now there's a critical point on that: famously, every major app is in total disagreement and disentanglement from every other famous app in that field. It's chaos/hell!!!

"Everyone knows" that Unity are "completely f'ing it up" viz a viz Autodesk products (after all - everyone uses Autodesk products, right?) and indeed "everyone knows" that Unity are "completely f'ing it up" viz a viz Unity3D" (after all - everyone users Unity3D right?)

(It really took me a full YEAR to get in to my fingers rotation, etc, with unity's key combos. Infuriating!)

You often hear 3D dudes talking about what a nuisance it is getting finger memory on various products since there is hopelessly no standards or even coincidental alignments.

So, this is worth bearing in mind in terms of your question: in the 3D field (where modified-mouse is used inherently and constantly) there is notoriously NO such standards!