Diagrammatic representation of the SASI-Seq process. Amplicons of a reference sequence (here we use PhiX174) are generated with unique barcodes at their 5’ end. Sets of amplicons with different barcodes are added to each sample that is destined for sequencing. The SASI fragments stay with the sample through library prep and can be detected after sequencing. SASI-Seq thus verifies which sample the sequence data originated from. FA, FB and FC represent the forward primers for the 214, 397 and 568 bp SASI fragments respectively, with SASI barcodes at the 5’ end shown here in red. R is the reverse SASI fragment primer also having a SASI barcode at the 5’ end, here coloured in red. Primer sequences are detailed in Methods.