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From SNPedia

GRCh38 is the Genome Reference Consortium Human genome build 38. As of May 7, 2014 it is the standard reference assembly sequence used by NCBI. Unlike other sequences, GRCh38 is not from one individual's genome sequence, but is built from reference sequences of different individuals. As genome build 38 is relatively recent, most testing services and researchers still use genome build 37 or build 36 as their reference assembly. In particular, positions on the various reference assembly sequences are very different, and gene mappings and orientations sometimes also vary.

SNPs in SNPedia are usually mapped by User:JlickBot to whatever is currently used by dbSNP's eutilities interface. As of May 7, 2014 this is GRCh38 38.1/141. Some SNPs may show an older assembly, genome build or dbSNP build. This may be because the SNP mapping is otherwise unchanged in the current build, the SNP is no longer mapped in the current build, or the SNP has not yet been updated. Sometimes the web interface to dbSNP may show a newer build than is available through the eutilities interface.

NCBI Genome Remapping Service may be helpful if you need to map to/from a different genome build.

See also GRCh38/orientation bug

These 84 snps were previously in snpedia under an earlier build, but appear to have been impacted by an orientation change with ambiguous flip in GRCh38: