> For the complete documentation index, see [llms.txt](https://webauthn-doc.spomky-labs.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://webauthn-doc.spomky-labs.com/v4.8/webauthn-in-a-nutshell/extensions.md).

# Extensions

{% hint style="info" %}
This page is about an advanced feature. You can skip it if you are new with Webauthn
{% endhint %}

The mechanism for generating public key credentials, as well as requesting and generating Authentication assertions, can be extended to suit particular use cases. Each case is addressed by defining a registration extension.

Standard extensions are usually listed in the dedicated IANA Registry available at <https://www.iana.org/assignments/webauthn/webauthn.xhtml>

{% hint style="warning" %}
This library is ready to handle extension inputs and outputs, but no concrete implementations are provided, except for the `appid` extension.

It is up to you, depending on the extensions you want to support, to create the extension handlers.
{% endhint %}


---

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