A monorepo (short for "monolithic repository") is a single version control repository (such as Git) that stores the code for multiple projects or services. In contrast to a "multirepo," where each project or service is maintained in its own repository, a monorepo contains all projects in one unified repository.
Shared Codebase: All projects share the same codebase, making collaboration across teams easier. Changes that affect multiple projects can be made and tested simultaneously.
Simplified Code Synchronization: Since all projects use the same version history, it's easier to keep shared libraries or dependencies consistent.
Code Reusability: Reusable modules or libraries can be shared more easily between projects within a monorepo.
Unified Version Control: There's centralized version control, so changes in one project can immediately impact other projects.
Scalability: Large companies like Google and Facebook use monorepos to manage thousands of projects and developers within a single repository.
Build Complexity: The build process can become more complex as it needs to account for dependencies between many different projects.
Performance Issues: With very large repositories, version control systems like Git can slow down as they struggle with the size of the repo.
A monorepo is especially useful when various projects are closely intertwined and there are frequent overlaps or dependencies.