The potential of leveraging digital data to support biodiversity conservation is widely recognized, yet data retrieval from digital platforms is not straightforward. Species-level digital identifiers, which are unique representations of species in digital platforms, can help to structure, retrieve, and integrate relevant information but their availability across digital platforms remains unclear. We examined digital species identifiers from over 500 digital platforms linked to multiple knowledge domains and assessed their availability for more than 1.5 million species across all major taxonomic groups. Our analysis revealed substantial variation in species representation across platforms. While many species are recognized in digital platforms linked with the life sciences and general knowledge, only a minority is featured in platforms associated with the social sciences, arts and humanities, or technology. Species coverage is also highly uneven between taxonomic groups. Birds, mammals, and flowering plants are relatively well represented, but other taxonomic groups tend to be represented in very few platforms which limits the potential for cross-platform data integration. These findings highlight major gaps in the representation of global biodiversity on digital platforms. Addressing these disparities will enable a more comprehensive, automated, and integrated use of digital data for conservation.