# Extensions

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This page is about an advanced feature. You can skip it if you are new with Webauthn
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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>

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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.
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