GUIDE-seq relies on the integration of double-stranded oligodeoxynucleotides (DSOs) into DSBs. It belongs to a family of methods—such as HTGTS, LAM-HTGTS, and Digenome-seq —that are aimed at detecting off-target effects of CRISPR/Cas9 and other RNA-guided nucleases (RGNs). RGN-induced DSBs are tagged by integration of blunt-ended DSOs in the genomes of living human cells. The DSO integration sites are mapped precisely in the genome at the nucleotide level with unbiased amplification and NGS.