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

# Accepting Additional Fields

> Create additional fields on the fly

The `allowAdditionalFields` feature offers a fluid integration experience, allowing users to effortlessly map to new or unconfigured fields in your Blueprints.

## How it works

* By enabling `allowAdditionalFields`, your Sheet isn't restricted to the initial configuration. It can adapt to include new fields, whether they're anticipated or not.
* These supplementary fields can either be added through API calls or input directly by users during the file import process.
* To ensure clarity, any field that wasn't part of the original Blueprint configuration is flagged with a `treatment` property labeled `user-defined`.
* When adding a custom field, there's no need to fuss over naming the field. The system intuitively adopts the header name from the imported file, streamlining the process.

In essence, the `allowAdditionalFields` feature is designed for scalability and ease, ensuring your Blueprints are always ready for unexpected data fields.

## Example Blueprint w/ `allowAdditionalFields`

```json theme={null}
{
  "sheets": [
    {
      "name": "Contacts",
      "slug": "contacts",
      "allowAdditionalFields": true,
      "fields": [
        {
          "key": "firstName",
          "label": "First Name",
          "type": "string"
        },
        {
          "key": "lastName",
          "label": "Last Name",
          "type": "string"
        },
        {
          "key": "email",
          "label": "Email",
          "type": "string"
        }
      ]
    }
  ]
}
```