# Authentication Tokens

As we have previously mentioned, an **Authentication Token** is an alphanumeric string generated through the Biuwer interface or via API, which is uniquely related to a basic user and is the element by which each user will be identified from the web application. external to Biuwer. For this reason, accompanying each resource, it is necessary to indicate the authentication token.

It is possible to implement **authentication token refresh policies**, manually or automatically via API, since the same user can have one or more tokens concurrently and each token allows a temporary validity interval to be established. For example, you could set an authentication token:

* Without any refresh policy.
* With a monthly refreshment periodicity.
* With a daily refreshment periodicity.
* Single use, for each session started from your application, if you need it.

<figure><img src="/files/tYJXxR6GdwRXzvgF5hvC" alt=""><figcaption><p>An authentication token is an alphanumeric string associated with a user with a validity period</p></figcaption></figure>


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