Here is a summary of the text in one paragraph, covering key points: Your customer list is a prized possession for marketers, serving as a tool to nurture contacts into buyers and grow your social media audience. Meta custom audiences allow you to target existing contacts and visitors with ads on Facebook, Instagram, and other Meta technologies, without costing extra. There are four types of custom audiences: website, app activity, engagement, and customer list. Customer list custom audiences let you target customers from a uploaded list, and can be used to create lookalike audiences that deliver ads to users similar to those in the original audience. To upload your customer list to Meta, head to Ads Manager, select Custom Audience, and choose Customer List as the source, formatting the data correctly before uploading. You can also automate updates using Zapier, adding new subscribers or contacts to your custom audience from various sources.