Cache Task Results

It's costly to rebuild and retest the same code over and over again. Nx has the most sophisticated and battle-tested computation caching system to make sure it never rebuilds the same code twice. It knows when the task you are about to run, has been executed before, so it can use the cache to restore the results of running that task.

If you want to learn more about the conceptual model behind Nx's caching, read How Caching Works.

Define Cacheable Tasks

To enable caching for build and test, edit the targetDefaults property in nx.json to include the build and test tasks:

nx.json
{
  "targetDefaults": {
    "build": {
      "cache": true
    },
    "test": {
      "cache": true
    }
  }
}

Cacheable operations need to be side effect free

This means that given the same input they should always result in the same output. As an example, e2e test runs that hit the backend API cannot be cached as the backend might influence the result of the test run.

Now, if you run a build task twice, the second time the operation will be instant because it is restored from the cache.

Nx restores both

the terminal output
the files & artifacts created as a result of running the task (e.g. your build or dist directory)

Keep reading to learn how to fine-tune what gets cached.

Fine-tune Caching with Inputs and Outputs

Detect Inputs and Outputs

Nx can automatically set inputs and outputs for you based on your tooling configuration settings when you use inferred tasks

Nx's caching feature starts with sensible defaults, but you can also fine-tune the defaults to control exactly what gets cached and when. There are two main options that control caching:

Inputs - define what gets included as part of the calculated hash (e.g. files, environment variables, etc.)
Outputs - define folders where files might be placed as part of the task execution.

You can define these inputs and outputs at the project level (project.json) or globally for all projects (in nx.json).

Take the following example: we want to exclude all *.md files from the cache such that whenever we change the README.md (or any other markdown file), it does not invalidate the build cache. We also know that the build output will be stored in a folder named after the project name in the dist folder at the root of the workspace.

To achieve this, we can add an inputs and outputs definition globally for all projects or at a per-project level:

nx.json
{
  "targetDefaults": {
    "build": {
      "inputs": ["{projectRoot}/**/*", "!{projectRoot}/**/*.md"],
      "outputs": ["{workspaceRoot}/dist/{projectName"]
    }
  }
}

Note, you only need to define output locations if they differ from the usual dist or build directory which Nx automatically recognizes.

Learn more about configuring inputs including namedInputs.

Where is the Cache Stored?

The cache is stored in .nx/cache by default. You can also change where the cache is stored if you want.

Enable Remote Caching

You can enable remote caching (Nx Replay) by connecting to Nx Cloud. To connect Nx to Nx Cloud run the following command:

❯

npx nx connect

Learn more about remote caching.

Turn off or Skip the Cache

If you want to ignore the cache (both reads and writes), use the --skip-nx-cache flag:

❯

nx build header --skip-nx-cache

Alternatively if you want to disable caching for a particular task, just make sure it is not part of the cached tasks. If you're using Nx Cloud, you might want to use --no-cloud to skip remote caching.

Clear the Local Cache

To clear the local cache, run:

❯

npx nx reset

For more details refer to the nx reset page.

Migration