The Index of Developmental Observations (IDOB) aims to codify milestones and other developmental systems into discrete elemental developmental observations, allowing conversion between systems, quality assurance, and widespread research. In its current form, IDOB is a set of 728 discrete developmental observations, mapped to 1,094 developmental milestones originating from four commonly used milestone sources.

IDOB does not seek to offer a new set of milestones for the purposes of screening. Observations themselves are not associated with an age or stage at which they should be met, but are associated with the milestone from which they were derived. IDOB seeks to be a partner resource for milestone systems and clinical screeners, allowing the results of evaluations to be more concretely tracked, compared, and collated.