> For the complete documentation index, see [llms.txt](https://docs.ngsurvey.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ngsurvey.com/form-management/security/security-items/cas-authentication.md).

# CAS Authentication

## 🔐 What is CAS authentication ?

Using the [central authentication service](https://en.wikipedia.org/wiki/Central_Authentication_Service) (CAS) you can enable single-sign-on on your ngSurvey forms using a CAS server to authenticate the respondents.

The CAS security item will automatically redirect the respondent to the CAS server if it can't find any ticket. If a ticket was found but the ticket was invalid it will ask the respondent to log back into the CAS server.

## 🔅 CAS properties

* **`CAS URL`**&#x55;RL of the server hosting your CAS. eg: <https://yourdomain.com/cas> &#x20;
* **`Allow multiple submissions`** can a respondent take part multiple time to the same survey.
* **`Login message`** is the message that will be shown to the respondent on the login page that will allow him load the CAS server login page. This message will be shown if ngSurvey fails to authenticate automatically the user.


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