synopkg/site/src/faq/sync-engines-in-monorepo.mdx

Consistent dependency versions in large JavaScript Monorepos

---
title: Manage npm engines throughout monorepo
---


Add the [`engines`](HREF_ENGINES) property of package.json files to also be inspected by synopkg.

### 1. Add a custom type

I've chosen a name of `engines` but it can be anything you like.

```jsonc title=".synopkgrc.json"
{
  "customTypes": {
    "engines": {
      // ^ this is your custom name
      "path": "engines",
      "strategy": "versionsByName",
    },
  },
}
```

### 2. Look for mismatches

Perform a one-off check of all versions defined under `engines` in your monorepo.

```bash
synopkg list --dependency-types engines
```

If the versions are not identical, they can be synchronised to all use the highest of the semver versions currently in use.

```bash
synopkg fix-mismatches --dependency-types engines
```

### 3. Track them in future

Add your new custom type to your `dependencyTypes`.

```json title=".synopkgrc.json"
{
  "dependencyTypes": [
    "dev"
    "engines"
    "peer"
    "prod"
  ]
}
```

Now when you run any synopkg command, versions under `engines` will also be checked.

```bash
synopkg list
```

### 4. Relax the rules (optional)

If you don't want the Node.js version to be identical in every package but do want them all to be compatible with each other, you can use a [Same Range](VERSION_GROUP_SAME_RANGE) Version Group. This defines an exception which only applies to Node.js, leaving anything else found under `engines` unaffected.

```json title=".synopkgrc.json"
{
  "dependencyTypes": [
    "dev"
    "engines"
    "peer"
    "prod"
  ],
  "versionGroups": [
    {
      "dependencies": ["node"],
      "dependencyTypes": ["engines"],
      "policy": "sameRange"
    }
  ]
}
```