Detects, normalizes, classifies, and extracts scholarly identifier strings. Provides lightweight, dependency-free helpers for twenty identifier types, including DOIs, ORCID iDs, ISBNs, ISSNs, arXiv and PubMed identifiers, ROR and ISNI, OpenAlex and ADS bibcodes, RRID, ARK, SWHID, and selected life-science accessions (UniProt, RefSeq, SRA, GEO, BioProject, and genome assemblies). Functions are vectorized, predictable, and suitable as low-level building blocks for other R packages and data workflows. Use scholid_types() for the authoritative type list. For online lookup, conversion, metadata retrieval, and linked identifier discovery, see scholidonline'.