In order to track online attention to a research output it needs to have at least one persistent scholarly identifier. Altmetric supports a range of identifiers:
DOIs
PubMed IDs
ISBNs
Handles
arXiv IDs
ADS IDs
SSRN IDs*
RePEC IDs
URNs
ClinicalTrials.gov records
*SSRN IDs are not supported by the Altmetric Explorer search function.