API — IT definition

An API (Application Programming Interface) is a technical contract that lets two pieces of software communicate without knowing each other's internals. Concretely, an API exposes a set of endpoints that other applications call to read data, trigger actions, or subscribe to events. It is the layer that turns a collection of applications into a coherent information system.

APIs have become the common language of modern IT. A Slack trigger, a Stripe payment, a Google login via SSO, an integration between your ERP and your CRM — every one of those interactions runs over an API. Without them, every integration would have to be hand-coded, and most SaaS platforms would be impossible to connect to the rest of the IT estate.

How an API works

An API rests on three pillars:

• •The contract: documentation that describes endpoints, accepted parameters, response shapes, and error codes. This is the shared language between vendor and consumer.
• •Authentication: API keys, OAuth tokens, mTLS — the mechanism that proves the caller is allowed to call.
• •Transport: usually HTTPS with a payload format (JSON, XML, GraphQL, gRPC, Protobuf).

A typical call looks like: "GET https://api.example.com/v1/users/42 with token X". The server returns a structured response the caller can parse and act on.

API styles

• •REST: the most common style. Stateless, resource-oriented (`/users`, `/invoices`), uses HTTP verbs (GET, POST, PUT, DELETE). Simple to grasp, ideal for public APIs.
• •GraphQL: a single endpoint, the client picks exactly which fields it needs. Reduces REST over-fetching, popular in modern mobile and web frontends.
• •gRPC: binary, Protobuf-based, very fast. Reserved for internal microservice traffic.
• •SOAP: legacy XML protocol, still present in banking, insurance, and legacy ERPs.
• •Webhooks: the inverse pattern — the vendor calls the client when an event fires. Essential for real-time integrations.

Why APIs matter to the CIO

For a CIO, APIs are not a purely technical topic — they are strategic leverage:

• •Interoperability: there is no information system urbanization without APIs. They are the tissue that connects ERP, CRM, ITSM, BI, HRIS, and business tools.
• •Cost control: avoid duplicate integrations, prefer vendors with open APIs over closed solutions.
• •Security: every exposed API is an attack surface. API-driven breaches at Optus, Twitter, T-Mobile have routinely outstripped classic breaches since 2022.
• •[Shadow IT](/en/glossary/shadow-it): public APIs let any business user plug Zapier or Make into a SaaS tool without IT approval.

Public, private, and partner APIs

• •Private (internal) APIs: used only inside the company to connect its own systems.
• •Partner APIs: exposed to a controlled circle of partners under contract (integrators, marketplaces).
• •Public APIs: open to any developer after sign-up, often monetized per usage (Stripe, OpenAI, Twilio).

The "API-first" pattern — designing the API before the UI — has become the norm at modern SaaS vendors.

Securing and governing your APIs

API governance best practices include:

• •Strong authentication: OAuth 2.0, signed JWTs, regular key rotation.
• •Rate limiting: cap calls per minute to prevent abuse and DoS.
• •Versioning: maintain multiple versions (`/v1`, `/v2`) so client integrations don't break.
• •Internal catalogue: inventory every API the company exposes — the blind spot of most IT teams.
• •Monitoring: track latency, errors, volume through an API gateway (Kong, Apigee, AWS API Gateway).

Kabeen automatically detects API-connected applications across your IT estate and surfaces the invisible dependencies between your tools.