> ## Documentation Index
> Fetch the complete documentation index at: https://www.marqeta.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Field Filtering

> Use field filtering when calling Marqeta's Core API to return only the requested fields in the response body.

The Core API supports field filtering for most `GET` requests. Append the `fields` parameter to your request URL to return only the requested fields in the response body.

<h2 id="_query_parameters">
  Query parameters
</h2>

| Fields                                       | Description                                                                                                                                                                                                  |
| -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| fields<br /><br />string<br /><br />Optional | Specify a comma-delimited list of fields to return (`field_1,field_2`,…​). Omit this field to return all fields.<br /><br />**Allowable Values:**<br /><br />All alpha-numeric characters, plus `-` and `_`. |

<Note>
  **Note**\
  Commas simultaneously delimit fields and nesting levels. The order in which you specify fields is insignificant in regards to nesting level. For example, the following sample request URL will return these four fields, provided all four fields exist: `field_1`, `field_1.field_2`, `field_2`, and `field_2.field_1`.
</Note>

<h2 id="_sample_request_url">
  Sample request URL
</h2>

```html HTML lines wrap theme={null}
https://api.marqeta.com/v3/campaigns?fields=field_1,field_2
```