BACKGROUND: The combined use of restriction enzymes with PCR has revolutionized molecular cloning, but is inherently restricted by the content of the manipulated DNA sequences. Uracil-excision based cloning is ligase and sequence independent and allows seamless fusion of multiple DNA sequences in simple one-tube reactions, with higher accuracy than overlapping PCR. RESULTS: Here, the addition of a highly efficient DNA polymerase and a low-background-, large-insertion- compatible site-directed mutagenesis protocol is described, largely expanding the versatility of uracil-excision DNA engineering. CONCLUSIONS: The different uracil-excision based molecular tools that have been developed in an open-source fashion, constitute a comprehensive, yet simple and inexpensive toolkit for any need in molecular cloning.