The barcode errors histogram shows the number of reads with difference levels of basecalling errors in this barcode:

• First field: The number of reads that have 0 basecalling errors (949782 in this example). This is the number of reads that perfectly match this barcode (in base space).

• Second field: The number ofreads that have one basecalling error(24584 in this example).

• Third field: The number of reads that have two basecalling errors(3935in this example).

From the 3935 value with 2 basecalling errors, we know that if we reanalyze with the number of allowed errors set to 1 instead of 2, then 3935 fewer reads will be assigned to this barcode.

? "barcode_errors_hist": [ 949782, 24584, 3935 ],

This histogram is typical of a real barcode. A large majority of reads are perfect matches, a few have one error, and a smaller number have two errors.

If the pattern is reversed (with very few perfect matches, some reads with one error, and many reads with 2 errors), we suspect that this is probably a fake barcode.