Provided herein are systems, compositions, and methods for the incorporation of unnatural amino acids into proteins via nonsense suppression or rare codon suppression. Nonsense codons and rare codons may be introduced into the coding sequence of a protein of interest using a CRISPR/Cas9-based nucleobase editor described herein. The nucleobase editors are able to be programmed by guide nucleotide sequences to edit the target codons in the coding sequence of the protein of interest. Also provided are application enabled by the technology described herein.