Correction to: Nature Biotechnology https://doi.org/10.1038/s41587-019-0134-y, published online 20 May 2019.

In the version of this article initially published, another technique for CBEs should have been included in the sentence “The activity window of base editors in mammalian cells has proven surprisingly difficult to broaden, with multimeric deaminase assembly for CBEs33 and extended guide RNAs for ABEs34 representing the only window-broadening strategies reported to date.” Linker variation31 has been added. The error has been corrected in the PDF and HTML versions of this article.