Sapling is a source control system developed and used at Meta that places special emphasis on usability and scalability. Git and Mercurial users will find many of the basic concepts familiar, and that workflows like understanding your repository, working with stacks of commits, and recovering from mistakes, are substantially easier. When used in conjunction with the Sapling server and virtual filesystem (not yet available publicly), Sapling scales to repositories with 10’s of millions of files, commits, and branches. While inside Meta it is primarily used for our large monorepo, the Sapling CLI also supports cloning Git repositories and can be used by individual developers to work with GitHub, etc.