monorepos

A monorepo (monolithic repository) is a version-controlled repository that contains the code for many projects, libraries, and services in a single repository. This contrasts with a polyrepo, where each project resides in its own repository. Monorepos are used to enable cross-project changes, unified tooling, and shared dependencies.

Benefits include atomic cross-project changes, unified tooling and build systems, centralized dependency management, easier refactoring across components, and greater visibility into cross-team changes. A monorepo can support consistent licensing, testing, and release processes across the codebase.

However, scaling a monorepo introduces challenges. Build and test times can grow, requiring advanced build systems and caching. Tooling must support large repositories and fast partial checks. Access control, code ownership, and change management become more complex. Migration and team coordination require effort.

Common practices include modular repository layout, clear ownership and codified approval processes, and selective checking. Modern monorepo toolchains such as Bazel, Buck, and Pants enable incremental builds, hermetic testing, and cross-language dependencies. Linting, code review, and automated dependency update systems help manage quality in large repos.

Adoption varies by organization. Some teams benefit from monorepos when code sharing and consistent tooling are priorities; others prefer polyrepos to reduce central bottlenecks. Several large technology companies use monorepos, including Google and Facebook, and several open-source projects adopt Bazel and related workflows.