API: What Purpose Does It Serve
API (Application Programming Interface) is a way for different programs to exchange data with each other according to predefined rules. An API explains how one application can request functions or data from another.
What is API
To explain in simple terms, you can think of API as a waiter in a restaurant. The menu in the restaurant is a set of options (functions) that the kitchen (the internal system) can provide. The customer (the user) places an order with the waiter (the API), who passes the request to the kitchen and then brings back the dish. The waiter doesn’t need to know the recipes or the details of preparation—only what was ordered and how to deliver the final result. In a similar way, an API receives a request from one program, sends it to another system, and returns the response. Programs don’t need to know each other’s internal structure—they communicate through a clear set of commands and data.
Another simple example: the weather app on a smartphone “contacts” the meteorological service’s server through an API. The server stores a weather forecast database, and the API allows the app to request the necessary information and display the latest forecast on the screen. The user only sees the final data (the weather forecast), while all the technical requests happen behind the scenes through the API interface.
Another simple example: the weather app on a smartphone “contacts” the meteorological service’s server through an API. The server stores a weather forecast database, and the API allows the app to request the necessary information and display the latest forecast on the screen. The user only sees the final data (the weather forecast), while all the technical requests happen behind the scenes through the API interface.
How API works
The principle of an API is that applications exchange requests and responses according to predefined rules. For example, one application (the client) wants to obtain data from another application (the server). Instead of accessing the server’s database or code directly, the client sends a request through the API.
The API receives the request, checks its validity and access rights, and then passes it to the server’s internal system. There, the required operation is executed, after which the result is sent back through the API. The client receives the response and uses it without needing to understand how everything works internally.
The API receives the request, checks its validity and access rights, and then passes it to the server’s internal system. There, the required operation is executed, after which the result is sent back through the API. The client receives the response and uses it without needing to understand how everything works internally.
Types of APIs
APIs come in different types depending on their area of application and level of openness:
- Internal (private) APIs are used within a company or product to enable interaction between internal modules. Access to such interfaces is restricted, and external developers cannot use them. For example, a bank’s internal database and its mobile application communicate through a private API that is inaccessible from outside.
- External (public) APIs are interfaces that a company provides to third-party developers for integration. They allow external services to access limited functions or data of your system. Examples include social network APIs (such as Facebook*), mapping and geolocation APIs (such as Google Maps), and payment APIs. Such interfaces are documented and published so that anyone (under the given terms) can use them in their applications.
- Partner APIs represent an intermediate category: access is granted to selected partners or clients under an agreement. They are not fully public but not completely closed either, and are often used for business-to-business (B2B) integrations.
In addition, APIs differ by the way they facilitate interaction. In the past, the term could refer to a library of functions in an operating system or application (for example, WinAPI in Windows for accessing OS functions). Today, however, APIs most often refer to web interfaces—that is, interaction over a network (usually the Internet) using standard web protocols (HTTP/HTTPS).
API methods and request formats
For different applications to communicate through an API, standard methods (commands) and data formats are used in requests. In the context of web APIs, the main methods correspond to operations for reading and modifying data. The most common ones are:
- GET — retrieve data (for example, request user information or a list of products).
- POST — send new data (for example, create a new record or place an order).
- PUT — replace or update existing data.
- PATCH — partially update data (similar to PUT, but only modifies specified fields).
- DELETE — remove data.
These methods are standardized in the HTTP protocol and supported by most APIs. Each method is directed to a specific API endpoint (URL) that identifies a resource. For example, the request “GET https://api.example.com/users/123” may mean “retrieve the data of the user with ID 123”. In response, the API will either return the user data (for instance, in JSON format) or a status code (such as 404 if the user does not exist, or 401 if access is denied).
In addition to methods, the structure of requests and responses is also important. Data is usually transmitted in JSON format because of its readability and compactness. XML or other formats are also used, but JSON has become the de facto standard for REST APIs. Requests may require authentication—most often through an API key or token. This is a unique string of characters that you obtain from the service to prove that you are authorized to access its API. Without the correct key, the service will simply return an access denial. This system protects data and helps control the load on the API.
In addition to methods, the structure of requests and responses is also important. Data is usually transmitted in JSON format because of its readability and compactness. XML or other formats are also used, but JSON has become the de facto standard for REST APIs. Requests may require authentication—most often through an API key or token. This is a unique string of characters that you obtain from the service to prove that you are authorized to access its API. Without the correct key, the service will simply return an access denial. This system protects data and helps control the load on the API.
How API integration works
API integration is a way of connecting different programs so they can automatically exchange data. To put it simply, one system communicates with another through a clear interface, sending or receiving the necessary information without manual effort.
Today, almost all services work this way: data flows from one program to another immediately, according to strict rules and in the correct format.
Unlike manual copying or file uploads, API integration provides a reliable and fast channel for data exchange. For example, a mobile application retrieves data from a cloud database, while a company’s website automatically receives fresh updates from the CRM. Each program remains independent, yet interacts with others to function more fully and conveniently.
Today, almost all services work this way: data flows from one program to another immediately, according to strict rules and in the correct format.
Unlike manual copying or file uploads, API integration provides a reliable and fast channel for data exchange. For example, a mobile application retrieves data from a cloud database, while a company’s website automatically receives fresh updates from the CRM. Each program remains independent, yet interacts with others to function more fully and conveniently.
Examples of API usage in business and marketing
APIs are used both in consumer applications and in business systems. Here are several examples where they play an important role:
- Log in using social media accounts. Many websites offer the option to log in using a Google or Facebook account. This works thanks to social networks’ OAuth APIs. When you click the login button, the site sends a request to the API to verify the data and retrieve the necessary profile information. As a result, you log in without registering, and the site receives your email and name.
- Online payments. If an online store accepts payments through PayPal or another service, the payment system’s API comes into play. Order details are transferred through it, a secure payment page opens, and after the transaction is completed, the store receives a notification. All parties exchange data according to clear and secure rules.
- Mapping services. Taxi and delivery apps may embed Google Maps. Using the API, they request coordinates, routes, and travel times. For example, by entering points A and B, you receive the optimal route and cost estimate. In logistics, map APIs are used to track parcels and determine courier locations in real time.
- Data aggregators. Aggregator websites, such as ticket or hotel search platforms, work through partner APIs. When a user enters parameters, the platform requests prices and availability from airlines and hotels. The results appear in a single window and update automatically.
- Analytics and advertising integration. In marketing, APIs are often used for data exchange. For example, the Google Analytics API transmits website metrics into a company’s reports. With advertising platform APIs, marketers can export statistics or upload audiences. This reduces manual work and helps keep data up to date.
- Connecting CRM and marketing services. Imagine a new lead in a CRM automatically triggering a welcome email campaign. The CRM sends the data to an email marketing service via an API, which queues the mailing. Then, delivery and open rate information is sent back to the CRM. This creates a unified customer interaction chain.
What is CRM? What types exist and who can benefit from such a system? Read here.
Why APIs are important and what they bring to business
| Advantage | Description | What It Brings to Business |
|---|---|---|
| Scalability and development speed | Using ready-made APIs instead of building functions from scratch | Faster development, reduced costs, flexible module updates without the need to redesign the entire system |
| Ecosystem integration | Connecting different applications into a unified environment | A single data space, smoother customer experience, synchronization across company departments |
| Process automation | Data exchange and task execution without employee involvement | Fewer errors, less routine work, more time for analytics |
| Security and access control | Clear separation of rights and protection of internal data | Reduced risks, encryption, request monitoring, protection of critical systems |
| New opportunities and revenue | Opening APIs to partners or external developers | Expanded audience, creation of new services, additional revenue streams |
Conclusion
An API is the foundation on which the interaction of different programs relies today. Without it, there would be no familiar super-apps, marketing platforms, or fast data exchange between services.
For a marketer, it is important to understand APIs not in terms of technical details, but as a tool that helps connect the necessary data and functions from other systems and combine them into a single chain. In digital marketing, where numerous services are used—CRM, analytics, advertising platforms, email campaigns—it is the API that ties everything together into one functioning ecosystem.
For a marketer, it is important to understand APIs not in terms of technical details, but as a tool that helps connect the necessary data and functions from other systems and combine them into a single chain. In digital marketing, where numerous services are used—CRM, analytics, advertising platforms, email campaigns—it is the API that ties everything together into one functioning ecosystem.
*Product of Meta, a company recognized as an extremist organization in the Russian Federation.
