A monorepo is a single version-control repository that holds many projects together, rather than splitting each project into its own repo. A web app, a mobile app, a backend service, and the shared libraries they all depend on can live side by side with one shared history. Big engineering organizations have used this model for years, and in 2026 it is common at all sizes because the tooling that keeps a monorepo fast has matured. It is a structural choice with real benefits and real costs, not a silver bullet.
How a monorepo works
In a monorepo, the repository root contains multiple project folders, often a packages or apps directory, plus shared configuration. Everything is checked out together, so a developer pulls the whole codebase at once. Because all the code shares one commit history, a single commit can change a shared library and every project that uses it in one atomic step.
This is the key mechanic: there is one version of any shared code at any moment. You never have one app on version 3 of a library and another stuck on version 1, because they all reference the same source. The projects inside are often built and shipped as containers, so a single repository can still produce many independently deployed services.
Monorepo versus polyrepo
| Aspect |
Monorepo |
Polyrepo (many repos) |
| Sharing code |
One source, atomic updates |
Publish and version packages |
| Visibility |
Search and refactor everywhere |
Scattered across repos |
| Setup overhead |
Higher, needs build tooling |
Lower per repo |
| Access control |
Coarser by default |
Fine-grained per repo |
| Best fit |
Related projects, shared code |
Independent teams and products |
Neither is universally correct. A polyrepo keeps each project simple in isolation; a monorepo makes coordination across projects far easier at the cost of needing tooling to stay fast.
The real benefits
- Easy code sharing. A shared component or utility lives in one place, used everywhere, always the same version.
- Atomic cross-project changes. Change an API and every consumer in one commit, so nothing is half-updated.
- One place to search and refactor. Find every use of a function across all projects at once.
- Consistent tooling. One lint config, one test setup, one formatter for the whole codebase.
The real costs
- You need build tooling. Running every test on every change does not scale. Tools like Nx, Turborepo, and Bazel cache builds and run only what changed.
- The repo gets large. A big history can slow cloning and some Git operations without care.
- Access control is coarser. Limiting who can touch which project takes more effort than separate repos give for free.
- A bad shared change has wide blast radius. Atomic updates are powerful but mean a mistake in shared code can affect everything at once.
How to decide
- Count the related projects. Several apps and services that share code lean toward a monorepo. One standalone app does not need one.
- Look at how often code is shared. Frequent shared changes favor a monorepo; fully independent products favor polyrepo.
- Be honest about tooling appetite. A monorepo without a smart build system gets slow. If you will adopt Nx or Turborepo, the benefits land.
- Consider team structure. Independent teams shipping on separate schedules sometimes prefer the isolation of separate repos.
What to skip
- A monorepo for a single small project. The tooling overhead is not worth it; a normal repo is fine.
- Running all tests on every commit. Use a tool that detects what changed and tests only the affected projects.
- Treating it as all-or-nothing. Many organizations run a couple of monorepos grouped by domain rather than one giant one.
FAQ
Is a monorepo the same as a monolith?
No. A monorepo is about how code is stored, one repository for many projects. A monolith is about how an application is built and deployed, as one unit. You can have microservices in a monorepo or a monolith in its own repo.
Do big companies use monorepos?
Several very large engineering organizations have used the monorepo model for years, which is part of why the supporting tooling is so mature.
What tools make a monorepo work?
Build and task runners such as Nx, Turborepo, and Bazel handle caching and running only the affected projects, which keeps a large monorepo fast.
When should I not use a monorepo?
For a single small project, or for fully independent products owned by separate teams with no shared code, where the coordination benefits do not apply.
Where to go next
See what a package manager is, npm versus yarn compared, and GitHub versus GitLab compared.