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title: Certificate Authorities
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[API Reference](https://developers.cloudflare.com/api/typescript)

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# Certificate Authorities

#### Certificate AuthoritiesHostname Associations

##### [List Hostname Associations](https://developers.cloudflare.com/api/typescript/resources/certificate_authorities/subresources/hostname_associations/methods/get)

client.certificateAuthorities.hostnameAssociations.get(HostnameAssociationGetParams {zone\_id, mtls\_certificate\_id } params, RequestOptionsoptions?): [HostnameAssociationGetResponse](<https://developers.cloudflare.com/api/typescript/resources/certificate_authorities#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_get_response%20%3E%20(schema)>) {hostnames }

GET/zones/{zone\_id}/certificate\_authorities/hostname\_associations

##### [Replace Hostname Associations](https://developers.cloudflare.com/api/typescript/resources/certificate_authorities/subresources/hostname_associations/methods/update)

client.certificateAuthorities.hostnameAssociations.update(HostnameAssociationUpdateParams {zone\_id, hostnames, mtls\_certificate\_id } params, RequestOptionsoptions?): [HostnameAssociationUpdateResponse](<https://developers.cloudflare.com/api/typescript/resources/certificate_authorities#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_update_response%20%3E%20(schema)>) {hostnames }

PUT/zones/{zone\_id}/certificate\_authorities/hostname\_associations

##### ModelsExpand Collapse

<details>

<summary>

TLSHostnameAssociation {hostnames, mtls\_certificate\_id }

</summary>

hostnames?: Array&lt;string&gt;

<a href="#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20tls_hostname_association%20%3E%20(schema)%20%3E%20(property)%20hostnames">Link to this property</a>

mtls\_certificate\_id?: string

The UUID for a certificate that was uploaded to the mTLS Certificate Management endpoint. If no mtls\_certificate\_id is given, the hostnames will be associated to your active Cloudflare Managed CA.

maxLength36

minLength36

<a href="#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20tls_hostname_association%20%3E%20(schema)%20%3E%20(property)%20mtls_certificate_id">Link to this property</a>

</details>

[Link to this property](<#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20tls_hostname_association%20%3E%20(schema)>)

<details>

<summary>

HostnameAssociationGetResponse {hostnames }

</summary>

hostnames?: Array&lt;string&gt;

<a href="#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_get_response%20%3E%20(schema)%20%3E%20(property)%20hostnames">Link to this property</a>

</details>

[Link to this property](<#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_get_response%20%3E%20(schema)>)

<details>

<summary>

HostnameAssociationUpdateResponse {hostnames }

</summary>

hostnames?: Array&lt;string&gt;

<a href="#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_update_response%20%3E%20(schema)%20%3E%20(property)%20hostnames">Link to this property</a>

</details>

[Link to this property](<#(resource)%20certificate_authorities.hostname_associations%20%3E%20(model)%20hostname_association_update_response%20%3E%20(schema)>)