====== Device and Transmitted Variables ======

The functional module "Device and Transmitted Variables" is used in SoSci Survey like a question but does not produce a visible output in the questionnaire for the respondents. Similar to [[:en:create:questions:internal]], this question type is responsible for storing data in the dataset. The question type "Device and Transmitted Variables" essentially serves two functions:

  - Storing information about the browser and device in the dataset.
  - Storing data in the dataset that was passed to the questionnaire when the [[:en:survey:url|URL to the questionnaire]] was accessed.


===== Information about the Device and Interview =====

Internet browsers typically transmit some information to web servers, such as the type of browser being used and the operating system it runs on ("browser identification"). In addition, SoSci Survey can retrieve additional information about the end device using JavaScript, such as screen size.

**Note:** The information transmitted by the browser and collected via JavaScript can be altered by the participant. For example, privacy plugins restrict the information significantly, and Apple does not see the need for Safari to distinguish between a MacBook (laptop) and an iPad (tablet). Therefore, the information should always be interpreted with caution.

To collect information, select the desired options (e.g., "screen size") in the question and place the question on a page of the questionnaire.

Information obtained through the browser identification is directly available below the question [[:en:create:functions:value]]. Information that needs to be collected via JavaScript is available on the following page of the questionnaire, similar to respondents' answers.

**Warning:** If you collect participants' IP addresses (Identification tab), your data quickly falls into the realm [[:en:general:dsgvo|Personal Data]], which is strictly regulated by the GDPR. Please clarify the legality of data processing in this case.

===== Transmitted Data =====

The questionnaire link can be supplemented with additional data. In fact, the link consists of the actual address and a query string separated by question marks with additional data (more on this in [[:en:survey:panels]])). The question type "Device and Transmitted Variables" can read and store this data in the dataset.

===== Use =====

To save a parameter from the URL:

  * Create a question with the question type "Device and Transmitted Variables.",
  * Go to the //Variables (POST/GET)// tab,
  * In the //Variable name (1)// field, enter the name of the parameter as used in the link,
  * Save the changes ({{:button.save.png?nolink|button to save changes}}),
  * Note the dataset variable name from the // Name column in the dataset// and
  * Place the question on the first (!) page of the questionnaire.

So, for example, if you add the parameter ''panelID=12345'' to the link (''%%https://www.soscisurvey.en/example/?panelID=12345%%''), please enter "panelID" in the //Variable name (1)// field to save it in the dataset. The value "12345" will then be stored in the dataset when the link is accessed. You can find the name of the variable under which it is saved (e.g., "GD01_RV1") in the question in the //Name column in the dataset//.

===== Data in the Link =====

If your questionnaire link is, for example, URL ''%%https://www.soscisurvey.en/example%%'', you can add a parameter ''r'' as follows:

<code>
https://www.soscisurvey.de/example/?r=alpha
</code>

The ''r'' parameter is a special case; SoSci Survey automatically stores it in the variable REF ([[:en:survey:url#einen_link_markieren_r|Einen Link markieren]]).

Multiple parameters in the query string are linked with an ampersand (&), for example:

<code>
https://www.soscisurvey.en/example/?r=alpha&user=12345
</code>

**Important:** The link is not (!) updated in SoSci Survey itself but at the time of sending the link, for example, via email.

**Important:** When customizing links individually, you can enter the realm of [[:en:general:dsgvo|Personal Data]]. Please clarify the legality of data processing in advance.

**Warning:** When using Outlook and other email programs, be careful that an HTML link consists of two parts: the linked URL and the displayed text. If you modify a link in the email program afterward, often only the displayed text is changed, but the link still points to the previous URL, as follows: [[https://www.soscisurvey.en/|https://www.example.com]]. Be cautious when copying and modifying email texts.

Which parameters SoSci Survey automatically processes in the link is described in the manual [[:en:survey:url]]. If you use other parameters, then use the question type "Device and Transmitted Variables."