Opening a library

iPhoto Library Manager lets you manage multiple iPhoto libraries, but only one of your libraries can be open in iPhoto at any given time. In your list of libraries, whichever library has a green checkmark appearing next to it is the active iPhoto library. Opening iPhoto, either by using the “Open iPhoto” button in iPhoto Library Manager, or by clicking on iPhoto in the Finder or on the dock, will display the active library in iPhoto.

To switch to another library, just double click the library's icon in iPhoto Library Manager, and it will take care of quitting iPhoto, changing the active library, and then reopening iPhoto to display the library that you double clicked. iPhoto Library Manager keeps a separate copy of your iPhoto preferences for each of your libraries, and will swap the preferences whenever it switches to a different library. This allows you to have different settings in the iPhoto preferences window on a per-library basis.

If you have iPhoto 8 or later, you can also simply double click the library itself in the Finder to open that library up in iPhoto. Be aware though that this does not work with iPhoto 7 - double clicking the library will not open the library you clicked, instead it will just open whichever library was last opened in iPhoto. This can be confusing, since you can double click one library but end up seeing another library's contents. Also, using this method will not swap out the iPhoto preferences like iPhoto Library Manager does when switching libraries.