Description
In the context of 3GPP standards, an Application Programming Interface (API) is a formally specified interface that defines how different software components, network functions, or external applications can interact with each other. It provides a contract that specifies the methods of communication, including the data formats (requests and responses), the operations that can be invoked, and the underlying protocols (often RESTful HTTP or gRPC). APIs abstract the complex internal implementations of network functions, exposing well-defined capabilities as reusable services. This abstraction is fundamental to service-based architectures (SBA) adopted in 5G Core (5GC), where Network Functions (NFs) like the AMF, SMF, and UDM interact via service-based interfaces, which are essentially a set of standardized APIs.
The architecture of 3GPP APIs is meticulously documented in technical specifications, detailing everything from the API endpoint URLs and HTTP methods (GET, POST, PUT, DELETE) to the exact JSON or XML schema of the messages exchanged. Key components include the API producer (the network function that hosts and implements the API), the API consumer (the entity invoking the API), and the API management layer, which may handle aspects like authentication, authorization, rate limiting, and analytics. APIs are often described using machine-readable formats like OpenAPI Specification (OAS), enabling automated code generation and validation. They operate over the Service-Based Interface (SBI) within the 5G Core, utilizing HTTP/2 for transport and JSON for payload serialization, ensuring efficient and flexible communication.
The role of APIs in the network is multifaceted. Internally, they enable the modular, decoupled design of the core network, allowing operators to deploy and upgrade Network Functions independently. Externally, they are the mechanism for service exposure, allowing authorized third-party application providers (e.g., in enterprise, IoT, or edge computing scenarios) to access network capabilities like quality of service (QoS) management, location information, or network status in a controlled manner through frameworks like the Network Exposure Function (NEF). APIs are also critical for network management and orchestration, enabling automated provisioning, configuration, and lifecycle management of network resources as part of broader frameworks like ETSI NFV-MANO. Ultimately, APIs transform the network from a static infrastructure into a programmable platform, fostering innovation and new service creation.
Purpose & Motivation
The standardization of APIs within 3GPP was motivated by the need to move away from monolithic, vendor-specific network architectures towards open, interoperable, and software-driven systems. Prior to widespread API adoption, network functions communicated via rigid, point-to-point, protocol-specific interfaces (often based on binary protocols like SS7 or Diameter), which made integration complex, slowed innovation, and created vendor lock-in. The purpose of defining common APIs is to solve these problems by establishing a universal 'language' for software components to communicate, thereby enabling multi-vendor interoperability, faster service deployment, and network agility.
Historically, the concept gained significant traction with the rise of web technologies and cloud-native principles. The shift to all-IP networks and the demand for Internet-style programmability drove 3GPP to embrace RESTful APIs and service-based architectures, particularly from 4G Evolved Packet Core (EPC) for certain interfaces and fully in the 5G Core. APIs address the limitation of previous 'closed' systems by providing a standardized, well-documented, and often HTTP-based method for interaction, which is familiar to a vast ecosystem of software developers. This lowers the barrier to entry for innovation, allowing both network operators and external developers to create new applications and services that leverage the unique capabilities of mobile networks, such as low latency, high bandwidth, and mobility support.
Furthermore, APIs are essential for enabling key 5G paradigms like network slicing, edge computing, and massive IoT. They provide the necessary hooks for orchestration systems to instantiate and manage end-to-end network slices on demand. They allow edge applications to request specific network treatments. In summary, APIs exist to transform telecom networks into open platforms, solving problems of integration complexity, operational rigidity, and limited service innovation, thereby unlocking the full economic and technological potential of 3GPP systems.
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (559 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the introduction of the Northbound API framework established standardized interfaces for network functions like the AUSF and PCF. This release specifically defined security procedures for API invoker onboarding and offboarding, and implemented detailed API versioning management, including corrections to API naming, resource presentation, and status codes.
- Introduce the Northbound API charging TS 32.240CR0394
- Security requirements for API invoker onboarding and offboarding TS 33.122CR0005
- Correction for the details of service API information TS 23.222CR0013
- Correction for usage of service API identification information TS 23.222CR0014
- API version TS 29.508CR0023
- API version update for Rel-15 TS 29.508CR0033
+ 13 more changes
In Release 16, the enhancements for the API function introduced a formalized architecture to support multiple third-party API providers, including new requirements for their publishing, discovery, operation, administration, and charging. Key new capabilities included procedures for API provider domain function registration, API sharing and invocation request routing with topology hiding for CAPIF interconnection, and updates to specific service APIs like Nnwdaf_EventsSubscription to support analytics for service experience and abnormal behavior. This release also defined mechanisms for service API discovery across multiple Common API Framework (CCF) entities and specified the serving area for APIs within the CAPIF interconnection model.
- Architecture functional model to support multiple API providers TS 23.222CR0012
- Service API publish and discovery requirements for 3rd party API providers TS 23.222CR0015
- Charging requirements for 3rd party API providers TS 23.222CR0016
- OAM requirements for 3rd party API providers TS 23.222CR0017
- API publish and API discover for CAPIF interconnection TS 23.222CR0035
- Update API invoker API list TS 23.222CR0039
+ 41 more changes
In Release 17, the API framework was significantly expanded, primarily through new and enhanced service APIs for the Network Data Analytics Function (NWDAF). Key introductions included the new Nnwdaf_DataManagement and Nnwdaf_MLModelProvision service APIs, while existing APIs like Nnwdaf_EventsSubscription and Nnwdaf_AnalyticsInfo received extensions for analytics including user data congestion, NF load, dispersion, WLAN performance, and redundant transmission experience. Furthermore, the release added API support for Application Enablement Function (AEF) location and an API invoker interface for edge applications, alongside extensions for the 5G Media Streaming (5GMS) architecture via eMBMS.
- Support AEF location and API invoker interface for edge application TS 23.222CR0078
- [5MBP3] API Extensions for 5GMS via eMBMS TS 26.347CR0013
- Nnwdaf_DataManagement Service API TS 29.520CR0290
- Nnwdaf_MLModelProvision Service API TS 29.520CR0293
- Complete definition of the Nnwdaf_MLModelProvision API TS 29.520CR0295
- Extension to User Data Congestion Analytics in Nnwdaf_EventsSubscription API TS 29.520CR0314
+ 92 more changes
In Release 18, key API enhancements included the introduction of new service APIs such as Eees_EASDiscovery, Eees_EASInformationProvisioning, and Eees_UEIdentifier, alongside expanded capabilities for existing APIs like Nausf_UEAuthentication, Npcf_SMPolicyControl, and the Nnwdaf suite with OAuth2 scope support and new analytics for PFD Determination, UE Mobility, and DN performance of Group UEs. The release also focused on improving API authorization and invocation procedures, including mechanisms for API invokers to obtain authorization from a resource owner and reducing consent inquiries in nested API calls. Furthermore, updates were made to service API management, such as adding a new Service KPI Information Element to publish requests and enabling service API status monitoring.
- API invoker obtaining authorization from resource owner TS 23.222CR0093
- Reducing resource owner consent inquiry in a nested API invocation TS 23.222CR0095
- API invoker clarification TS 23.222CR0100
- New IE(Service KPI) in Service API publish request TS 23.222CR0102
- Service API status monitoring TS 23.222CR0111
- Eees_EASDiscovery API: request for EAS selection support TS 24.558CR0017
+ 191 more changes
In Release 19, key API enhancements focused on the Common API Framework (CAPIF) with the introduction of an API invoker split into frontend and backend components, finer granularity of access control for service APIs, and new procedures for API invoker onboarding and authorization based on the purpose of data processing. The release also introduced new service APIs like the `Sdd_URLCCTransmissionConnection` API for the SDDM-S and added support for signalling storm analytics to the `Nnwdaf_EventsSubscription` and `Nnwdaf_AnalyticsInfo` APIs. Furthermore, it provided mechanisms for resource owner consent upon service API invocation and enabled a UE-deployed API invoker to access resources of other UEs within a group.
- Slice-based service API exposure TS 23.222CR0131
- Update to API invoker Roles in CAPIF TS 23.222CR0202
- Finer granularity of access control for service API TS 23.222CR0206
- API invoker onboarding TS 23.222CR0214
- API invoker split into frontend and backend components TS 23.222CR0221
- Enhancement to API invoker Authorization with the Purpose of Data Processing TS 23.222CR0226
+ 191 more changes
In Release 20, the primary new development for the API function was the introduction of an API exposure Reference architecture. This established a formal framework defining a set of API classes for developing applications and for providing system services to those applications within the NGN environment.
- API exposure Reference architecture TS 23.700CR0003
Explore further
Broader topics and technologies where API plays a role.
Defining Specifications
3GPP specifications that define or reference API, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 22.038 vj00 | USIM Application Toolkit (USAT) Stage 1 | Rel-19 |
| TS 22.057 vj00 | Mobile Execution Environment (MExE) Stage 1 | Rel-19 |
| TS 22.121 v1400 | Virtual Home Environment Requirements | Rel-5 |
| TS 22.127 v1900 | Open Service Access (OSA) Requirements | Rel-9 |
| TS 22.228 vj00 | IP Multimedia Service Requirements | Rel-19 |
| TR 22.907 v1312 | UMTS IC Card and Terminal Concepts | Rel-4 |
| TS 23.039 v1400 | SMSC to SME Interface Protocols | Rel-5 |
| TS 23.057 vj00 | Mobile Execution Environment (MExE) Specification | Rel-19 |
| TS 23.127 v1600 | Virtual Home Environment Stage 2 Specification | Rel-6 |
| TS 23.198 v1900 | Open Service Access (OSA); Stage 2 | Rel-9 |
| TS 23.218 vj00 | IMS Call Model Specification | Rel-19 |
| TS 23.222 vj80 | Common API Framework for 3GPP Northbound APIs | Rel-19 |
| TS 23.228 vj50 | IMS Stage-2 Service Description | Rel-19 |
| TS 23.479 vj00 | MBMS API for Mission Critical Services | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 23.701 vc00 | WebRTC Access to IMS Architecture Study | Rel-12 |
| TS 23.722 vf10 | Common API Framework (CAPIF) for 3GPP Northbound APIs | Rel-15 |
| TR 23.758 vh00 | Study on Edge Application Architecture | Rel-17 |
| TS 23.792 vg00 | MBMS API for Mission Critical Services | Rel-16 |
| TR 23.958 vj00 | EDGEAPP alignment with ETSI MEC and GSMA OP | Rel-19 |
| TS 24.523 vj00 | NGCN-NGN Interconnection Scenarios | Rel-19 |
| TS 24.543 vj50 | SEAL Data Delivery Management Protocol | Rel-19 |
| TS 24.558 vj50 | Edge Enabler APIs Stage 3 | Rel-19 |
| TS 24.559 vj41 | Application Data Analytics Enablement Services | Rel-19 |
| TS 24.560 vj00 | AIML Enablement (AIMLE) Services Stage 3 Protocol | Rel-19 |
| TS 25.211 vj00 | UTRA FDD Layer 1: Transport & Physical Channels | Rel-19 |
| TS 26.118 vj00 | Virtual Reality Media Formats | Rel-19 |
| TS 26.119 vj00 | XR Media Capabilities for AR Devices | Rel-19 |
| TS 26.142 vj00 | 3GPP TS 26.142: Dynamic and Interactive Multimedia Scenes (DIMS) | Rel-19 |
| TS 26.143 vj00 | 5G Messaging Media Types and Codecs | Rel-19 |
| TS 26.307 vj00 | 3GPP HTML5 Profile Specification | Rel-19 |
| TS 26.346 vj20 | MBMS User Services Media Codecs & Protocols | Rel-19 |
| TS 26.347 vj00 | MBMS Transport Protocol and API (TRAPI) | Rel-19 |
| TS 26.501 vj30 | 5G Media Streaming (5GMS) Architecture | Rel-19 |
| TS 26.510 vj10 | Media Delivery APIs for 5GMS and RTC Systems | Rel-19 |
| TS 26.511 vj00 | 5G Media Streaming Profiles, Codecs & Formats | Rel-19 |
| TS 26.567 vj00 | IMS-based Split Rendering | Rel-19 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TR 26.806 vi00 | Technical Report on Smartly Tethering AR Glasses | Rel-18 |
| TS 26.841 vj00 | Study on Media Messaging Enhancements | Rel-19 |
| TR 26.857 vi00 | Technical Report on Media Service Enablers | Rel-18 |
| TS 26.891 vg00 | Media Distribution Services in 5G System | Rel-16 |
| TR 26.907 vj00 | HTML5 for 3GPP Services Study | Rel-19 |
| TR 26.926 vj00 | Traffic Models & Quality Evaluation for Media/XR in 5G | Rel-19 |
| TR 26.928 vj00 | Study on eXtended Reality (XR) in 5G | Rel-19 |
| TR 26.942 vj00 | Study on Media Energy Consumption Exposure & Evaluation | Rel-19 |
| TR 26.948 vj00 | Video enhancements for 3GPP Multimedia Services | Rel-19 |
| TR 26.953 vj00 | Study on Service Interactivity for Streaming & Download | Rel-19 |
| TR 26.956 vj01 | Beyond 2D Video Formats & Codecs Study | Rel-19 |
| TR 26.981 vj00 | MBMS Provisioning & Content Ingestion Interface Study | Rel-19 |
| TR 26.998 vj00 | 5G AR/MR Glasses Integration Study | Rel-19 |
| TR 28.816 vh00 | Charging for 5G Cellular IoT | Rel-17 |
| TR 28.840 vi10 | Technical Report | Rel-18 |
| TR 28.843 vi10 | Technical Report on Charging Aspects for Vertical Scenarios | Rel-18 |
| TS 28.849 vj10 | CAPIF Phase2 Charging Study | Rel-19 |
| TS 28.851 vj10 | Charging for Next Gen Real Time Communication Phase 2 | Rel-19 |
| TS 29.116 vj00 | REST-based protocol for xMB reference point | Rel-19 |
| TS 29.198 v1900 | OSA API Overview Specification | Rel-9 |
| TS 29.201 vj00 | RESTful Rx Interface for AF-PC Communication | Rel-19 |
| TS 29.508 vj40 | 5G Session Management Event Exposure Service | Rel-19 |
| TS 29.509 vj50 | AUSF Service Based Interface Protocol | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.520 vj40 | 5G Network Data Analytics Services Stage 3 | Rel-19 |
| TS 29.523 vj20 | 5G Policy Control Event Exposure Service | Rel-19 |
| TS 29.525 vj40 | 5G UE Policy Control Service Stage 3 | Rel-19 |
| TS 29.549 vj40 | SEAL API Specification for Vertical Applications | Rel-19 |
| TS 29.591 vj40 | 5G NEF Southbound Services Stage 3 | Rel-19 |
| TS 29.817 vc10 | Study on XML-based Rx interface for PCC | Rel-12 |
| TS 31.131 vj00 | C Language Binding for (U)SIM API | Rel-19 |
| TS 31.213 vi30 | Test specification for (U)SIM | Rel-18 |
| TS 31.221 vj00 | Contact Manager Internal Interface for UICC | Rel-19 |
| TR 31.822 vi10 | Technical Report on GBA_U based APIs | Rel-18 |
| TS 32.101 vj00 | Management principles and high-level requirements | Rel-19 |
| TS 32.140 vj00 | Subscription Management (SuM) requirements | Rel-19 |
| TS 32.141 vj00 | Subscription Management (SuM) Architecture | Rel-19 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.829 va00 | Fault Management Alignment Study | Rel-10 |
| TS 32.831 va00 | 3GPP-TMF PM Alignment Study | Rel-10 |
| TS 33.117 vk00 | Catalogue of General Security Assurance Requirements | Rel-20 |
| TS 33.122 vj20 | Security Architecture for CAPIF | Rel-19 |
| TS 33.222 vj00 | Secure HTTP Access in GAA | Rel-19 |
| TR 33.739 vi10 | Study on security enhancement of support for | Rel-18 |
| TS 33.749 vj00 | Study on security aspects of edge computing enhancement | Rel-19 |
| TS 33.823 vc20 | GBA Web Browser Integration Study | Rel-12 |
| TR 33.882 vi01 | Technical Report on 5G Security for Personal IoT Networks | Rel-18 |
| TR 33.884 vi01 | Technical Report | Rel-18 |
| TS 34.131 vj00 | SIM API C Language Test Specification | Rel-19 |
| TS 38.843 vj00 | Study on AI/ML for NR Air Interface | Rel-19 |
| TS 51.013 vj00 | SIM API for Java Card Test Specification | Rel-19 |
