Tagging proteins with a functional sequence is a powerful way to access function, and inserting tags at endogenous genomic loci allows the preservation of a near-native cellular background. GFP11 is the 11th beta-strand of the superfolder GFP beta-barrel structure. When expressed in the same cell, GFP11 and its complementary GFP fragment (GFP1-10) enable functional GFP tagging upon complementation. The key advantage of the GFP11 is its small size (16 aa): this allows commercial ssDNA oligomers to be used as HDR donors, circumventing any requirement for molecular cloning.