# Tokens

## 🔐 What are tokens ?

Token are pre-generated unique values that can be used by respondents to access the survey. These tokens can be automatically generated using the [token generator](https://docs.ngsurvey.com/form-management/security/security-items/tokens/token-generator) or you can create or [import](https://docs.ngsurvey.com/form-management/security/security-items/tokens/token-generator) your own set of token values.

Once a token has been used by the respondent ngSurvey will link that token to the respondent responses to let you track down in the [respondent reports](https://docs.ngsurvey.com/form-management/respondents-management) the respondents based on the token they used.

As tokens are just text values you can easily distribute them to your respondents using any kind of electronic or non-electronic way from standard mail to phones or emails.

{% hint style="warning" %}
Each token can only be used one time by a respondent.
{% endhint %}

## 🔅 Tokens security properties

* **`Token source variable name`** is the browser querystring variable that holds the token value when you want that the token security item retrieves automatically the token from the browser's querystring. 
* **`Allow access to valid tokens only`** open the survey to respondent who don't have any tokens. If this option is enabled respondent without token will be able to take the survey several times while respondent with a valid token will only be able to submit once their answers.
* **`Hide login screen`** if no valid token has been found dont show to the respondent the user interface to enter the token.

{% hint style="success" %}
This security item can be used as a [key provider](https://docs.ngsurvey.com/form-management/security/key-provider-concepts). 
{% endhint %}