---
title: Caching
---

import Callout from "../../../components/callout";

# Caching

Unlike other tools you may have used, `turbo` can cache emitted files and logs of previously run commands. It does this so it can skip work that's already been done, yielding incredible time savings.

By default, [`turbo run`](../reference/command-line-reference#turbo-run-task1-task2-1) considers any files emitted in the `dist/**` or `build/**` folders of a package task (defined in that package's `package.json` `scripts` object) to be cacheable. In addition, `turbo run` treats logs (`stderr` and`stdout`), which are automatically written to `.turbo/run-<command>.log`, as a cacheable artifact. By treating logs as artifacts, you can cache just about any command in your Turborepo.

## Configuring Cache Outputs

Using [`pipeline`](../reference/configuration#pipeline), you can configure cache conventions across your Turborepo.

To override the default cache folder behavior, pass an array of globs to a [`pipeline.<task>.outputs`](../reference/configuration#outputs) array. Any file that satifies the glob patterns for a task will be treated as artifact.

```json
{
  "turbo": {
    "pipeline": {
      "build": {
        "outputs": ["dist/**", ".next/**"],
        "dependsOn": ["^build"]
      },
      "test": {
        "outputs": [], // leave empty to only cache logs
        "dependsOn": ["build"]
      }
    }
  }
}
```

If your task does not emit any files (e.g. unit tests with Jest), just set `outputs` to an empty array (i.e. `[]`). Turborepo will automagically cache the logs for you.

<Callout emoji="ℹ️">
  Pro Tip for caching ESLint: You can get a cacheable pretty terminal output
  (even for non-errors) by setting `TIMING=1` variable before `eslint`. Learn
  more over at the [ESLint
  docs](https://eslint.org/docs/1.0.0/developer-guide/working-with-rules#per-rule-performance)
</Callout>

With the above pipeline configuration and proper output folders, if you were to run:

```shell
# Run `build` npm script in all packages and apps and cache the output.
turbo run build test
```

And open up your `node_modules/.cache/turbo`, you should see the cached artifacts.

## Turn off caching

Sometimes you really don't need or want this cache behavior (such as when you're doing something with live reloading such as `next dev` or `react-scripts start`). To entirely disable caching, simply append `--no-cache` to any command:

```shell
# Run `dev` npm script in all packages and apps in parallel,
# but don't cache the output
turbo run dev --parallel --no-cache
```

You can also always disable caching on a specific task by setting `cache` to `false` in your Turborepo [`pipeline`](../reference/configuration#pipeline-1):

```json
{
  "turbo": {
    "pipeline": {
      "dev": {
        "cache": false
      }
    }
  }
}
```

## Force overwrite cache

Conversely, if you want to force `turbo` to re-execute a previously cached task, add the `--force` flag:

```shell
# Run `build` npm script in all packages and apps,
# ignoring cache hits.
turbo run build --force
```

## Logs

Not only does `turbo` cache the output of your tasks, it also records the terminal output (i.e. combined `stdout` and `stderr`) to (`<package>/.turbo/run-<command>.log`). When `turbo` encounters a cached task, it will replay the output as if it happened again, but instantly, with the package name slightly dimmed.

## Hashing

By now, you're probably wondering how `turbo` decides what constitutes a cache hit vs. miss for a given task. Good question!

First `turbo` constructs a hash of the current global state of the monorepo:

- The contents of any file that satifies the the glob patterns in [`globalDependencies`](../reference/configuration#globalDependencies-1)

Then it adds on more factors relative to a given package's task:

- Hash the contents of all not-gitignored files in the package folder
- The hashes of all internal dependencies
- The `outputs` option specified in the [`pipeline`](../reference/configuration#pipeline)
- The set of resolved versions of all installed `dependencies`, `devDependencies`, and `optionalDependencies` specified in a package's `package.json` from the root lockfile
- The package task's name

Once `turbo` encounters a given package's task in its execution, it checks the cache (both locally and remotely) for a matching hash. If it's a match, it skips executing that task, moves or downloads the cached output into place and replays the previously recorded logs instantly. If there isn't anything in the cache (either locally or remotely) that matches the calculated hash, `turbo` will execute the task locally and then cache the specified `outputs` using the hash as an index.

The hash of a given task is injected at execution time as an environment variable `TURBO_HASH`. This value can be useful in stamping outputs or tagging Dockerfile etc.

<Callout>
  As of `turbo` v0.6.10, `turbo`'s hashing algorithm when using `npm` or `pnpm`
  differs slightly from the above. When using either of these package managers,
  `turbo` will simply include the hashed contents of the lockfile in its hash
  algorithm for each package's task. It will _not_ parse/figure out the resolved
  set of all dependencies like the current `yarn` implementation.
</Callout>
