The default image viewer on Mac is Preview, a stock OS X app that actually originated at NeXT. Preview does many things. On top of letting you view, edit, and annotate images and PDF documents, Preview can also import and export documents to various file formats. It is, for many, a staple.
Being a default photo viewer, Preview will launch automatically if you open any image or PDF document on your Mac. As useful as it is, some users with specific needs will find this behavior more of an annoyance than a helpful feature, and would like to default to other apps for opening images. For example, you might want to make Photoshop your default image viewer and editor. Or maybe you want Pixelmator to be that go-to app.
Fortunately, you can easily change the default image viewer on your Mac. This is how to do just that.
How to stop using Preview as the default photo viewer
Step 1: Click to select an image file you want to open with a different photo viewer or editor. Once it is selected, hit Command + I on your keyboard to bring up the Info panel. Alternatively, you can simply right click on the file, and select Get Info.
Step 2: The Info panel will open with various details about the image. Under the Open With dropdown menu, select the application you want to use as default. It could be Photoshop, or in my case, it is Pixelmator. Assuming you want to apply the change to all similar file types, click Change All to open all documents like this one with the selected application in the future.
Step 3: You will be asked to confirm the change. Click Continue.
Step 4: Depending on your needs, you might have to repeat the process with different file types. In our example above, we are just switching the default image viewer for JPG files, but you’ll need to repeat the process for other files such as GIF, PNG, PDF, etc, depending on your preferences, of course.
You can just as easily revert back to Preview should you want to by simply following the steps above again.
The steps describe above work for any kind of files and applications. You can just as easily make specific file types open in specific apps.