# filter

> Source: https://docs.clonepartner.com/reference/steps/filter/

<!-- sources: src/steps/filter-step.ts, src/steps/base-step.ts, src/steps/types.ts, references/envoy/step-types.md -->

# filter

Keeps or drops each item based on a boolean JSONata predicate — the first-class way to remove items from a stream.

## When to use it

Use `filter` whenever some items should not continue down the pipeline. Do not use `skip_if`/`run_if` for this (they skip a step but pass the item through unchanged), and do not rely on a [transform](/reference/steps/transform/) returning `undefined` (which also passes the item through).

## Configuration

The config must be a single JSONata expression string. An object config fails validation with `Filter step config must be a JSONata boolean expression string`.

| Key | Type | Required | Default | Description |
|---|---|---|---|---|
| `config` | string | Yes | — | Boolean JSONata predicate evaluated per item with `{ input, arguments, steps, variables, job_config }`. Truthy keeps the item; falsy drops it. |

## Example

```yaml
name: active-users
connectors:
  source:
    type: csv
steps:
  - name: read_users
    type: call_method
    config:
      connector: source
      method: read
      args:
        resource: users

  - name: only_active
    type: filter
    config: 'input.status = "active"'
```

## Behavior notes

- **Truthy → the item passes through unchanged.** The filter never modifies the item.
- **Falsy → the item is dropped** — nothing is emitted downstream. This is a real drop, not a passthrough.
- **A predicate that resolves to JSONata "nothing" drops the item.** The step wraps your expression as `(<expression>) ? true : false`, so a missing field or a `null` result counts as falsy instead of triggering the base passthrough behavior for `null` configs.

## Related

- [transform](/reference/steps/transform/) — reshape items; note its `undefined` result does not drop
- [Task YAML schema](/reference/task-yaml/) — `run_if`/`skip_if`, which skip a step without dropping the item
- [Transforming and filtering](/building/transforming-and-filtering/) — when to filter versus skip