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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%5Fauthorities/subresources/hostname%5Fassociations/methods/get)

client.certificateAuthorities.hostnameAssociations.get(HostnameAssociationGetParams { zone\_id, mtls\_certificate\_id } params, RequestOptionsoptions?): [HostnameAssociationGetResponse](https://developers.cloudflare.com/api/typescript/resources/certificate%5Fauthorities#%28resource%29%20certificate%5Fauthorities.hostname%5Fassociations%20%3E%20%28model%29%20hostname%5Fassociation%5Fget%5Fresponse%20%3E%20%28schema%29) { hostnames } 

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

##### [Replace Hostname Associations](https://developers.cloudflare.com/api/typescript/resources/certificate%5Fauthorities/subresources/hostname%5Fassociations/methods/update)

client.certificateAuthorities.hostnameAssociations.update(HostnameAssociationUpdateParams { zone\_id, hostnames, mtls\_certificate\_id } params, RequestOptionsoptions?): [HostnameAssociationUpdateResponse](https://developers.cloudflare.com/api/typescript/resources/certificate%5Fauthorities#%28resource%29%20certificate%5Fauthorities.hostname%5Fassociations%20%3E%20%28model%29%20hostname%5Fassociation%5Fupdate%5Fresponse%20%3E%20%28schema%29) { hostnames } 

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

##### ModelsExpand Collapse 

TLSHostnameAssociation { hostnames, mtls\_certificate\_id } 

hostnames?: Array<string\>

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

HostnameAssociationGetResponse { hostnames } 

hostnames?: Array<string\>

HostnameAssociationUpdateResponse { hostnames } 

hostnames?: Array<string\>