Many e-commerce sites have a large number of campaigns and promotions running. Facets in Optimizely Customized Commerce let users apply filters to campaigns and discounts (promotions), for easier location of specific items in the **Campaign** view. 

Key components mentioned here are available in the EPiServer.Commerce.Shell.Facets namespace.

## FacetGroup

FacetGroup contains properties that identify a group of items by which to filter a campaign and settings to configure a group. Initialize a FacetGroup through a constructor.

## FacetGroup settings

FacetGroupSettings contains properties to configure a facet group. Initialize these properties through a constructor.

## FacetItem

FacetItem contains properties that identify a facet item in the facet group, which is a value to a filtered campaign. Initialize these properties through a constructor.

## Custom facets Commerce 12.10 and higher

To customize facet groups, create a class inheriting from FacetGroupModifier, then register it on one of your initialization modules.

**Example:** Displaying four markets by default in the market facet group, instead of three.

**Example:** Registering the facet.

## Custom facets Commerce 12.9 and lower

First, you need a custom facet based on a campaign facet. Here we create a custom facet that:

• Clears all built-in groups.

• Has a facet group that filters by a campaign's last modified date. This user can choose last modified day, week, or month.

This example shows that the last modified facet group is single selection with three options: day, week, or month.

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Note

To show a item numbers that indicate how many campaigns are filtered, in FacetGroupSettings, set showMatchingItemsto **true**.

To use a CustomFacet, follow these steps.

1. Create a rest store named "**customfacet**" that returns a custom facet.

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Note

To show matching items, use the facet query handler to calculate matching numbers.

2. Register the custom facet store and override the existing store "**epi.commerce.facet**". Create a module initializer. If an initializer exists, edit it.

3. If you do not register a module initializer, you need to update or create the project's _module.config_ file, as shown in the example below.

After following the steps above, the **Campaign** view has a custom facet on the left side, and the built-in groups have disappeared. We can interact in the UI, but still need to filter campaigns.

4. Create a function to filter campaigns by last modified date, based on GetContentsByFacet.

5. Customize the query to return GetCampaignsByLastModified, by overriding GetSalesCampaignChildrenQuery. 

Here is an example of the customized **Campaign** view.