Question: What is a barcode whitelist?
Answer: A barcode whitelist is the list of all known barcode sequences that have been included in the assay kit and are available during library preparation.
For example, there are roughly 737,000 cell barcodes in the whitelist for Cell Ranger's Single Cell 3' and V(D)J applications. Here are the first 10 lines of the corresponding barcode whitelist 737K-august-2016.txt:
AAACCTGAGAAACCAT
AAACCTGAGAAACCGC
AAACCTGAGAAACCTA
AAACCTGAGAAACGAG
AAACCTGAGAAACGCC
AAACCTGAGAAAGTGG
AAACCTGAGAACAACT
AAACCTGAGAACAATC
AAACCTGAGAACTCGG
AAACCTGAGAACTGTA
You can find the barcode whitelist file bundled inside your Cell Ranger installation, e.g. cellranger-2.1.0/cellranger-cs/2.1.0/lib/python/cellranger/barcodes/737K-august-2016.txt