---
id: plugin-filter
title: 'Filter Plugin'
---

## What's a filter plugin? {#whats-a-filter-plugin}

:::caution

Filter plugins are **experimental** and requires more users feedback

:::caution

### When to use a filter plugin? {#when-to-use}

If you need to mutate the metadata for different reasons this is a way to do it, all manifest request are intercepted, but the tarballs, user, profile or tokens requests are not included. A good example to review is the [verdaccio-plugin-secfilter](https://github.com/Ansile/verdaccio-plugin-secfilter).

### Plugin structure {#build-structure}

The plugin only has one async method named `filter_metadata` that reference of the manifest and must return a copy (or modified object but not recommended) of the metadata.

```ts
export default class VerdaccioMiddlewarePlugin implements IPluginStorageFilter<CustomConfig> {
  async filter_metadata(metadata: Readonly<Manifest>): Promise<Package> {
    // modify the metadata
    const newMetadata = { ...metadata, ...{ name: 'fooName' } };
    return newMetadata;
  }
}
```

### Configuration

Just add `filters` to the `config.yaml` file and your own plugin options.

```yaml
filters:
  storage-filter-blackwhitelist:
    filter_file: /path/to/file
```

More [info in the PR](https://github.com/verdaccio/verdaccio/pull/1161).