Genetic decoding is not 'frozen' as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational 'correction' of problem or 'savior' indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5' or 3' of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3' from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.This work was supported by grants from Science Foundation Ireland [12/IP/1492 and 13/1A/1853 to J.F.A; 12/IA/1335 to P.V.B.], US. National Institutes of Health [RO3 MH098688 to J.F.A.], the Wellcome Trust [106207 to A.E.F and 094423 to P.V.B.] and the European Research Council (ERC) grant No. 646891 to A.E.F.]This is the final version of the article. It first appeared from Oxford University Press via https://doi.org/10.1093/nar/gkw53