All variants are called against the hg38/GRCh38 reference. Below are locations of the public reference files in different formats.
FASTA: gs://genomics-public-data/references/hg38/v0/Homo_sapiens_assembly38.fasta
FAI: gs://genomics-public-data/references/hg38/v0/Homo_sapiens_assembly38.fasta.fai
DICT: gs://genomics-public-data/references/hg38/v0/Homo_sapiens_assembly38.dict
For more detailed information regarding the the genomic data, we recommend the following articles:
How the Genomic data are organized
All of Us Genomic Quality Report