[Home](./index.md) > [sip.js](./sip.js.md) > [UserAgentOptions](./sip.js.useragentoptions.md) > [sipExtensionReplaces](./sip.js.useragentoptions.sipextensionreplaces.md) ## UserAgentOptions.sipExtensionReplaces property Replaces header. https://tools.ietf.org/html/rfc3891 Signature: ```typescript sipExtensionReplaces?: SIPExtension; ```