Juxta is an open-source cross-platform tool for comparing and collating multiple witnesses to a single textual work. The software allows you to set any of the witnesses as the base text, to add or remove witness texts, to switch the base text at will, and to annotate Juxta-revealed comparisons and save the results.
Juxta presents several kinds of analytic visualizations. It can display a heat map of the textual variants that allows you to locate—at the level of any textual unit—all witness
variations from the base text.