The Global Scale for Early Development was field-tested and could offer a global solution to the need countries have for good metrics to track their progress toward early childhood development targets in the absence of reliable, freely accessible tools for population-level monitoring of children up to age three. The instruments were developed by a multidisciplinary team led by the World Health Organization. This work represents the harmonization of three already existing efforts: the Infant and Young Child Development Group, the Caregiver Reported Early Development Instruments Group, and the Global Child Development Group.