Change Keystroke Shortcut for Zoom In / Out

Change the Keystroke Shortcut for Zoom In / Zoom Out to COMMAND + AND COMMAND - like in Firefox and Preview.

you can easily change that yourself (like every menu-shortcut) via OS X Preferences>Keyboard&Mouse

Just add a shortcut, name it exactly like the menu entry and choose the keystrokes you like.


That request illustrates how interesting UI issues can be. It’s often assumed that the Mac UI does similar things when a command or procedure is used across different applications. That’s often true, and lends a sense of familiarity to those commands or procedures.

You cited the behavior of Command-+ in Firefox and in Preview. But does that keystroke command do the same thing in both applications? No, it doesn’t.

In Firefox, Safari and most browsers watch what happens when when Command-+ is invoked while viewing a page that includes text and images. The text grows larger, but images do not. Try this experiment: Use Command-+ to make the text of a displayed Web page quite large. Now copy a bit of that text to the clipboard and paste it into a TextEdit document. The result in TextEdit shows a large font size, much larger than the font size set as default in the browser, or intended by the Web page designer.

Now view a PDF document in Preview that has both text and images. Each time Command-+ is invoked, both the apparent text and image size grows. Do this several times until the text size looks quite large. Copy a bit of text to the clipboard and paste it into a TextEdit document. The text displayed in TextEdit isn’t as large as it now appears in Preview. The same would be true if we had copied an image from the Preview display. So Command-+ doesn’t do the same thing in Preview that it does in Firefox. Unlike the result in Firefox, it doesn’t change the font size of the text. In Preview, Command-+ zooms the apparent size of text and images without changing their actual size.

Let’s look at another Apple application, Pages. Click anywhere in a Pages document and invoke Command-+. Nothing happens. Select a block of text and press Command-+. The font size of the selected text is now larger. For Pages, Apple provides a different command that will zoom the displayed size without modifying the actual size of text and images; Command-> will do that.

So the same command, Command-+, produces different results in a browser (Safari), Preview and Pages. I won’t go into the UI differences in Apple’s Professional applications except to say that different conventions and commands are used in them. Apple makes no pretense of using Command-+ as a command that works in the same way across the universe of Mac applications.

Let’s talk about DEVONthink, which uses Apple’s Cocoa text routines. A text document in DEVONthink employs commands consistent with those of TextEdit. TextEdit uses Command-+ to make the font size of selected text larger. But TextEdit has no keyboard shortcut to zoom the view. So DEVONthink uses the keyboard shortcut Control-Command-Up/Down Arrow to zoom up/zoom down the view of text documents. Command-+ is reserved for increasing the font size of selected text.

I do a lot of writing inside my databases. Because I will often copy/paste my rich text documents into a more competent word processor for final polishing, I’ve set the default for text font and size, e.g., Times 12. But that’s a bit small when viewed onscreen. So I’ve told DEVONthink to zoom my documents, using the Control-Command-Up Arrow command. The apparent size of those documents is remembered next time I open them. That’s convenient. They are easier to read, but the font size wasn’t changed.

Speaking of convenience, why shouldn’t the same keyboard shortcut be used in DEVONthink to increase/decrease the zoom size of text, PDF and image documents, and to make the font size in HTML and WebArchive documents more readable? In looking at a list of search results, why should I remember to use different keyboard shortcuts depending on file type if I want to make the viewed size of text larger or smaller, whether the document is text, PDF, HTML or WebArchive? Is keyboard shortcut consistency for that purpose bad UI design? I don’t think so.

Tip: I recently saw a user complaint about small font size in Full Screen display. Just invoke Control-Command-Up Arrow while in Full Screen mode. The actual font size of text documents isn’t changed, but the text can be increased to a readable size, and this is useful for PDF, HTML and WebArchive documents as well.

Comment: Ergonomically, Control-Command-Up/Down Arrow is more comfortable than Shift-Command-=/Command–. Both are two-handed keyboard shortcuts but quickly shifting displayed text size up or down is more comfortable with Control-Command-Up/Down Arrow.

Comment: This may require some caution. For example, if the Zoom In/Zoom Out keyboard shortcuts for text documents were changed to Command-+/Command–, an ambiguity would result as those commands are used for modifying font size in selected text. The same commands would appear in the Format > Font menu and in the View menu. Further tinkering with keyboard commands would be required to resolve ambiguities. The result would be that one or the other of the “common” keyboard commands would be changed. So preconceived Mac consistency can’t be maintained. Which convention do you want to sacrifice?

Of course, as the Zoom In/Zoom Out commands are contextual by document type, one might try to change the keyboard shortcut just for PDF and HTML/WebArchive and image documents – leaving the existing commands for text documents (which could get very tricky). The downside of inconsistent zooming shortcuts for different document file types would be that one would have to adapt the shortcut used to the document type when browsing through a search results list.

In Pages, Apple chose to keep Command-+/Command-- for changing font size in selected text (which is familiar and is done frequently), and added a new shortcut, Command->/< to Zoom In/Zoom Out (an unfamiliar convention, but used for a setting which likely isn’t changed frequently). In Aperture 2.x, Apple uses the keyboard shortcut “f” to toggle between large/smaller views of photos – Command-+ and Command-- are not supported. One has to learn new UIs for the Apple Pro apps.

Thanks very much for the illuminating replies. Very useful! Since I’m both a newbie Mac user and Devonthink user, all very valuable information.