The present disclosure relates to a method of in vitro engineering of nucleic acids. This disclosure further relates to in vitro engineering of viral genomes and to the improvement of viral properties by in vitro genomic engineering of viral genomes. Specifically, the disclosure relates to in vitro viral genomic digestion using RNA-guided Cas9, the assembly of a recombinant genome by the insertion of a DNA or RNA fragment into the digested viral genome and transformation of a host cell with the recombinant genome. This method also related to in vitro engineering for error correction of nucleic acids.