# Externally provided variables

There are many cases where you might want to pass data into a form that would never be provided by the responder directly, like:

* tracking information, such as unique identifiers, account IDs, etc;
* configuration variables, which enable or disable certain functionality.

External variables are created in Formsort to capture parameters that are passed into a flow via the URL. 

{% hint style="info" %}
Consult the [URL parameters](https://docs.formsort.com/importing-data/url-parameters) page for more information on the proper format and other details.
{% endhint %}

If you're familiar with HTML form semantics, this is the equivalent of a `<input type="hidden">` field which is part of a form, but not provided by the user.

Much like a variable provided by a user, external variables can be used in [variable templating](https://docs.formsort.com/variable-templating), [conditional logic](https://docs.formsort.com/conditions-and-logic), and in functions for [locally-calculated variables](https://docs.formsort.com/response-data-collection-and-management/variable-schema/calculated-answers).&#x20;

## External variable setup

To use an external variable for URL parameter capture, in the **Variables** tab, select **Externally provided** > **Add External Variable**, and set the name of the expected URL parameter in the **Variable** name field.

For example, if a user is being directed into your Formsort flow with `utm_source` as a URL parameter, the URL will look something like this:&#x20;

`https://<YOUR_FLOW_URL>/?`**`utm_source={{example_utm_value}}`**

In order for Formsort to capture the value of `utm_source`, you need to create an external variable called `utm_source`. This variable will **automatically** store the value of the URL parameter when the flow loads.

<figure><img src="https://1036686854-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MJPnL__mOdr_mLZ8nwf%2Fuploads%2FimtrhtpatDxgWIKOV980%2Fimage.png?alt=media&#x26;token=a65f8eca-6f86-4c47-861d-52263961092e" alt=""><figcaption><p>Create an external variable called utm_source. See settings below</p></figcaption></figure>

{% hint style="info" %}
External variables are automatically included in answers payload delivery, if they are provided in the URL at flow load. No further configuration is needed once the form is deployed with the update :raised\_hands:
{% endhint %}

## Settings

### Is array

Use the **Is array** option if the field passed into the flow has an array format. For more information on the accepted query parameter convention, see [URL parameters](https://docs.formsort.com/importing-data/url-parameters#setting-array-answers).

### Required

When the **Required** field is enabled, two things will happen when the external variable is not passed in to a user session:&#x20;

* A warning will be logged to the browser console *during the user session*; and&#x20;
* An error field called **externalVarIssues** will be submitted in the `flowLoaded` event answer payload. This second point requires having an [analytics integration](https://docs.formsort.com/integrations/getting-data-out#sending-analytics-events) set up.&#x20;

{% hint style="info" %}
The **externalVarIssues** field is an object; see example:

`"externalVarIssues":{"ext_var_name":"missing"}`
{% endhint %}

### Keep in URL if present on load

When a flow is loaded in Formsort, any URL parameters that match any variable defined in the flow will be placed into the variables and removed from the URL. To learn more about that, read about getting data in from [URL parameters](https://docs.formsort.com/importing-data/url-parameters).

If you would like instead for a variable value to remain in the URL, enable **Keep in URL if present on load**. This might be helpful if you are matching up campaigns on a URL string, and want to keep things like the `utm_source` consistent across pages.

{% hint style="warning" %}
Anything in the URL will most likely be recorded by any analytics scripts you include in the integrations, so avoid enabling this setting for variables that set personally-identifying information.
{% endhint %}

### Storing answers in cookies

Another option is to store answers in cookies. In cases where you are collecting more sensitive information, this might be a better option, since you might not want to pass sensitive information unencrypted via URL. In order to do so, you can enable **Read/Write in Cookie** option.&#x20;

{% hint style="info" %}
Configuring a domain is required to store answers in cookies.
{% endhint %}

Take care when "start each session as a new responder" is enabled in your [Variant Settings](https://docs.formsort.com/form-behavior-settings/variant-settings), as the setting will remove Formsort-related cookies by default. See the **Prevent Editing** option below to guard against this.&#x20;

### Default value

When a **default value** is set, if a value is not present when a flow is loaded, the default value will be used.

A common use for this is to define control variables, similar to constants, that govern what parts of a flow are enabled, or function as a setting parameter.

### Prevent Editing

By default, external variables passed in as query parameters can be overridden in the flow. If, for example, `zip_code` is passed in as a query parameter, but a question then asks the user to enter their zip code to a variable `zip_code`, the external answer will be replaced by the submitted answer. If you want to ensure external answers passed in as query params **cannot** be overriden, enable the **Prevent Editing?** option.&#x20;

{% hint style="info" %}
**Prevent editing** can also be used to persist external variables that are read from/written to cookies, when "**start each session as a new responder**" is enabled.&#x20;

Read more about **start each session as a new responder** [here](https://docs.formsort.com/form-behavior-settings/variant-settings#behavior).&#x20;
{% endhint %}