CodonCode Aligner is a software for DNA sequence assembly, alignment, contig editing, and mutation detection. In addition to features common in sequence assembly programs like end clipping, alignments to reference sequences, and exporting, CodonCode Aligner offers many unique features not found in other software. CodonCode Aligner is easy to learn and use, yet powerful and highly customizable. It includes extensive, context-sensitive help with "how to" instructions and explanations about the algorithms used. CodonCode Aligner is widely used in phylogenetics, evolution research, bio-geography, mutation detection, and other biomedical research areas.