--- layout: default title: lowercase_string parent: Processors grand_parent: Pipelines nav_order: 45 --- # lowercase_string ## Overview Converts a string to its lowercase counterpart. `lowercase_string` is part of [mutate string](https://github.com/opensearch-project/data-prepper/tree/main/data-prepper-plugins/mutate-string-processors#mutate-string-processors) processors. Option | Required | Type | Description :--- | :--- | :--- | :--- with_keys | Yes | List | A list of keys to convert to lowercase.