The 2023 update of the Child Opportunity Index (COI 3.0) expands neighborhood-level data on children’s access to opportunity through 2023, incorporating enhanced indicators and improved data sources. This release refines measurement across 14 subdomains and standardizes values using the 2023 child population, offering a clearer picture of disparities in resources that shape children’s development. Because of methodological updates, results are not directly comparable to the earlier 2021 version.