There are a number of options to exclude certain products from running ads. The 3 most popular are 1) Using Facebook product sets, 2) Shopify collections, or 3) the Flexify metafield "status" - previously called "visibility". Keep in mind that the recommended approach is to export all your products to Facebook & filter on Facebook's end. (Approach 1)
1. Product sets #
This is the most common approach to exclude certain products from running ads. You can create a product set (e.g. based on a product tag or based on a collection handle) in your Facebook Commerce Manager (just access your Facebook catalog and Sets section). A product set is a subset of the products in your catalog. So while your feed/catalog will still include all products, you would exclude them at a later stage on Facebook before running ads.
A product set can be built by applying filter rules in a product catalog - each catalog can have many product sets.
See here for more details: https://developers.facebook.com/docs/marketing-api/reference/product-set#filterrules
In those filter rules, you can create product sets by e.g. availability, product type, vendor, or custom labels.
For example, if you want to create a product set only with products that are in stock, you just need to use the "is not" rule of "Availability" and the value "Out of stock" in the field (or the filtering rule "is" and the value "in stock"). Other possible values are "available for order" or "discontinued" which can be used with another filter.
2. Shopify Collection #
Another way to exclude certain products is to never include them in the feed in the first place. A simple way to do this is to create an automated Shopify collection where these products are excluded (e.g. include only products that have a quantity greater than 0) and then use this collection as the basis of your feed.
You can select the collection you want to use from the drop-down menu in your Flexify Settings Page on Shopify.
3. Flexify metafield "status", previously called "visibility" (paid feature) #
Sometimes you need to exclude products like gift cards, vouchers or samples from your Facebook catalog, but they still have to be available for purchase from your Shopify store.
In this case, you can hide products (only on the variant level) from your feed either using a metafield app (e.g. Matrixify app, Metafield guru) or the Shopify bulk editor link like so (please replace STORE_NAME with your Shopify domain):
https://admin.shopify.com/store/STORE_NAME/bulk?resource_name=ProductVariant&edit=metafields.flexify.status&show=full_title
Supported values for the metafield are: active, archived.
See here for more details.
Why export ALL products? #
Creating ads for your products is one thing, creating correctly targeted ads is another. For the targeting to work best, you want Facebook to train their algorithms on as many products as they can. Each product you tell Facebook about has a chance of creating events (e.g. cart abandonment) that will help improve the audience you target.