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# Choosing keepers with duplicate rules

iPhoto Library Manager uses a rule-based system to choose a keeper from each group of duplicate photos. The keeper will typically be the one photo that you want to keep around, with the rest of the duplicates getting moved to the trash, or having some other action performed on them. You can choose from several built-in duplicate rules using the pop-up menu down at the bottom of the window.

Once a rule has been chosen from the pop-up menu, iPhoto Library Manager will evaluate all the duplicate groups based on that rule. In the duplicate browser, you will see a white checkmark above whichever photo from each group has been chosen as the keeper.

The built-in duplicate rules include:

- Keep the most recently modified duplicate: compares the modification dates of the duplicate photos and will choose whichever one is the most recently modified. This rule is useful if you’re using the “Analyze original photos” option, but would prefer to keep edited versions of photos over the unedited versions.
- Keep duplicates from default library: this rule is useful if you are searching more than one library at a time. If two duplicates are found in different libraries, this rule will keep whichever duplicate is in your default iPhoto library, rather than the other copies of that photos that are in your other libraries. If your duplicate search does not include your default library, you should make a copy of this rule and customize it to specify which library’s photos you would like to keep.
- Keep duplicate with best metadata: compares several criteria of each photo, including the number of faces that have been identified in the photo, keywords that have been assigned to the photo, whether the photo has been assigned to a geographic location, and whether the photo has been given a custom title. Photos that contain more of this metadata will be chosen over other photos that don’t have this metadata assigned to them. If you have different copies of a particular photo, and you’ve done more face identification, keyword tagging, and so forth on some photos than others, then this rule can be helpful to choose the photo that you’ve done the most work on.
- Keep the largest duplicate: compares the file size of each duplicate photo and keeps whichever one is the largest. This is useful if you have some duplicates that have been scaled down from the original, so you can keep the largest copy and get rid of the smaller ones.

Editing rules

The built-in rules are a good start, but since everybody’s photo collection is unique, you may need to create a custom duplicate rule to choose keepers according to what makes the most sense for your own photos. To create a custom rule, click the rules pop-up menu and select “Edit Rules…” from the bottom of the menu. This will present you with the following window:

You can view (but not edit) the built-in rules to see how they are implemented. To create your own rule, click the gear button in the upper right and select “New Rule” from the menu that appears. If you’d like a rule similar to one of the built-in rules, select that rule from the pop-up menu, then click the gear button and select “Duplicate Rule” to make a copy of that built-in rule. You can specify a name for your new rule by typing it in the “Name” field.

Each duplicate rule is made up of one or more criteria that you'd like to use to compare the photos in each duplicate group. By evaluating these criteria, one or more photos from the group will be chosen as the keeper from that group. The criteria available to compare include the photos' rating, modification date, size, format, and much more. See the Criteria Details section for more information.

Because in many cases the duplicate photos will also have identical values for many of these attributes, you can specify multiple criteria to evaluate the photos by. If the first criteria is identical for some or all the photos in the group, the evaluation will then proceed to the second criteria, and so on, until they have all been evaluated.

How rules are evaluated

In the example above, we have three photos that have been identified as duplicates by iPhoto Library Manager, and the four criteria from the rule displayed above that were specified to evaluate the duplicate photos.

The first criteria says to choose whichever photo has the highest rating. However, all the photos have the same rating (0 stars), so this criteria does not choose any photos, and evaluation continues to the next criteria.

The second criteria says to prefer whichever photo has the newest modification date. Two of the photos have been edited and have the same modification date, but the photo in “Default Library” has an older modification date. So, this criteria narrows down the group from three photos to just the ones from MacBook Library and iMac Library, and then evaluation continues to the next criteria.

The third criteria says to prefer a photo that came from the library "iMac Library" over photos from other libraries. One of the two remaining photos is from the "iMac Library", so that photo is marked by this criteria as the chosen photo.

Since we have now narrowed down the group to a single photo, the fourth criteria is not needed, and is skipped. The photo from “iMac Library” is selected as the keeper, and will appear with a white checkmark over it in the duplicate browser.

Single vs multiple keepers

By default, only a single photo is marked as a keeper from each duplicate group. If your duplicate rule does not narrow things down to just a single photo, then iPhoto Library Manager will pick one of the remaining photos for you as the keeper. However, if you uncheck the “Always choose only a single keeper” checkbox, then all the photos that make it to the end of criteria evaluation will be marked as keepers.

For example, let’s say you have a duplicate group with two photos from “Library A”, and two photos from “Library B”, and that you have a duplicate rule set up with a single criteria that says “Library is Library A”. Both photos from Library B will be eliminated by the criteria, leaving just the two photos from Library A. If “Always choose only a single keeper” is checked, then iPhoto Library Manager will only mark one of the two photos from Library A as a keeper; if it is unchecked, then both photos from library A are marked as keepers.

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