IP Office provides Computer Telephony Integration (CTI) capabilities via the Telephony API. TAPI is a Microsoft interface that enables third party solutions deployed on Windows machines to apply first- and third-party control to calls.

The DevLink3 API was introduced in IP Office Release 10.0. DevLink3 supersedes the Delta2 record reporting used by the existing DevLink DLL. DevLink3 provides an enhanced, real-time stream of all call events. The stream can be consumed by client applications and used to track calls throughout their lifecycle.

DevLink provides a real-time event stream that can be consumed by client applications. The event stream incorporates Call records, which include call and party/target information. DevLink is superseded by DevLink3 in IP Office Release 10 and higher, and is not recommended for new development. DevLink remains available in Release 10.0 to give developers time to transition their existing solutions. Avaya cannot guaranteed that future releases of IP Office will continue to support DevLink. Developers are advised to upgrade their integration to DevLink3 as soon as possible.

The IP Office Centralized CTI Web Services API introduced in IP Office Release 10.1 offers an open platform for use in creating applications that employ telephony features and other functionalities provided by IP Office such as Call Log, Directory, Instant Messaging, Presence and Voicemail services. The API has a dependency on Avaya one-X Portal and is supported for use in a distributed IP Office environment.

The Location API was introduced in IP Office Release 10.0. The API enables developers to build custom emergency services solutions that can update the dynamic location of an extension that does not have a fixed location, such as a WiFi Cordless phone. In addition, the API supports On-site Notification functionality, enabling solutions to receive notification of emergency services calls and to get information about each call, including the caller's location, from the associated Emergency Services Call Alarm.

Avaya Client SDK Release 4.1 introduced initial support, including basic voice and video calling only, for IP Office Platform Release 11.0 / Powered by Avaya Release 3.0 and later. IP Office Release 11.1 supports Avaya Client SDK 4.5 which includes IP Office On Premise Messaging support. Note that Avaya Client SDK does not currently support VP8 video codec.

WebRTC capabilities were introduced in IP Office Release 10.0. The WebRTC SDK includes a JavaScript API that makes it easy for Web developers to build WebRTC clients that can be registered as SIP endpoint devices at IP Office extensions. Users can initiate, receive and control audio and video calls from a Web page displayed in a WebRTC-compliant browser, without having to install a plug-in. The WebRTC SDK supports Chrome and Firefox browsers. Note that Apple requires use of Safari browser for WebRTC support on iOS; the WebRTC SDK does not yet include Safari support - so there is no support for iOS with the WebRTC SDK at this time.

Introduced in IP Office Release 10.1, the IP Office Management API consists of a set of REST-based services which enables developers to consume IP Office configuration objects and incorporate configuration changes to an expanded set of IP Office entities into applications. Requests and responses utilize XML and JSON formats.

The Configuration Service enables IP Office configuration changes to be incorporated in client solutions via a Web service interface, expressing configuration changes via an XML document. The API is supported for use with IP Office Essential Edition, Preferred Edition, Advanced Edition and Server Edition only. Using the API, developers can build custom, Web-based front-ends for administering users and local groups.

The Service Monitoring Web Services introduced in IP Office Release 10.1 is a REST Web Services interface that provides read-only access to IP Office system status data in XML format. The data can be used by developer solutions for applications such as proactive resource monitoring or monitoring of the general health and inventory of a fleet of IP Office systems.

The MTCTI-3 Web Services introduced in IP Office Platform Release 11.1 provide an alternative to 3rd Party TAPI on Avaya IP Office. The protocol enables an application to observe call activity on users and queues, and acquire presence activity. A number of additional features beyond those available through TAPI are also supported by MTCTI-3.