Preimplantation genetic testing (PGT) is widely adopted to select embryos with normal ploidy but requires invasive embryo biopsy procedures. Therefore, non-invasive PGT (niPGT) detection of cell-free DNA (cfDNA) in blastocyst culture medium has gradually become a hot area in the field of assisted reproduction. This chapter will systematically summarize how researchers use embryonic cfDNA to conduct niPGT detection worldwide. It will also thoroughly review the factors that affect the accuracy of the test and its underlying issues, as well as prospective applications. We hope to provide a useful reference for the standardized operation of non-invasive PGT that can be widely applied in clinical practice.