Abstract: Provided herein are methods and compositions relating to variant nucleic acid libraries encoding for antibodies including single domain antibodies. Libraries generated using methods described herein have improved characteristics including improved binding affinity. Libraries described herein include variegated libraries comprising nucleic acids each encoding for a predetermined variant of at least one predetermined reference nucleic acid sequence. Further described herein are protein libraries generated when the nucleic acid libraries are translated. Further described herein are cell libraries expressing variegated nucleic acid libraries described herein.