Federal guidance allows Head Start (HS) grant recipients to submit applications to convert enrollment slots from HS services for preschool-age children to Early Head Start (EHS) services for pregnant women, infants, and toddlers. Applications must include data that demonstrate a need for EHS services, show how HS–eligible children will continue to be served, and illustrate how the program will avoid displacing currently enrolled HS children. This snapshot describes the most common data sources cited in applications to convert enrollment slots to center-based EHS to demonstrate community availability of early care and education (ECE) and need for services. We use the term availability to refer to the prevalence and enrollment capacity of ECE programs in a particular community. We use the term need to refer to potential HS or EHS demand from children and families seeking or eligible for services in a particular community. (author abstract)