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APIs 101: Introductions to APIs

API Testing

Shreya Srivastava

Apr 26, 2025

APIs are the backbone of modern software, enabling apps to communicate and share data seamlessly. Here's what you need to know:

What are APIs? APIs (Application Programming Interfaces) are rules that let software systems interact - like a translator for apps. Popular examples include Facebook's API (2006) and Twilio's API (2007).
How do APIs work? A client sends a request (via a URL, HTTP method, headers, and data). The server processes it and responds with a status code (e.g., 200 OK, 404 Not Found) and data.
Why are APIs important? They power social media, e-commerce, IoT, and more by reducing costs, speeding up development, and ensuring secure communication.
Key concepts: Endpoints (URLs for resources), HTTP methods (GET, POST, etc.), and security (OAuth 2.0, rate limits).

Pro Tip: Use AI tools for faster, scalable API testing with features like no-code test creation and auto-healing tests.

APIs are everywhere, handling 80% of web traffic. Whether you're building software or integrating services, mastering APIs is essential.

APIs are the backbone of modern software, enabling apps to communicate and share data seamlessly. Here's what you need to know:

What are APIs? APIs (Application Programming Interfaces) are rules that let software systems interact - like a translator for apps. Popular examples include Facebook's API (2006) and Twilio's API (2007).
How do APIs work? A client sends a request (via a URL, HTTP method, headers, and data). The server processes it and responds with a status code (e.g., 200 OK, 404 Not Found) and data.
Why are APIs important? They power social media, e-commerce, IoT, and more by reducing costs, speeding up development, and ensuring secure communication.
Key concepts: Endpoints (URLs for resources), HTTP methods (GET, POST, etc.), and security (OAuth 2.0, rate limits).

Pro Tip: Use AI tools for faster, scalable API testing with features like no-code test creation and auto-healing tests.

APIs are everywhere, handling 80% of web traffic. Whether you're building software or integrating services, mastering APIs is essential.

APIs are the backbone of modern software, enabling apps to communicate and share data seamlessly. Here's what you need to know:

What are APIs? APIs (Application Programming Interfaces) are rules that let software systems interact - like a translator for apps. Popular examples include Facebook's API (2006) and Twilio's API (2007).
How do APIs work? A client sends a request (via a URL, HTTP method, headers, and data). The server processes it and responds with a status code (e.g., 200 OK, 404 Not Found) and data.
Why are APIs important? They power social media, e-commerce, IoT, and more by reducing costs, speeding up development, and ensuring secure communication.
Key concepts: Endpoints (URLs for resources), HTTP methods (GET, POST, etc.), and security (OAuth 2.0, rate limits).

Pro Tip: Use AI tools for faster, scalable API testing with features like no-code test creation and auto-healing tests.

APIs are everywhere, handling 80% of web traffic. Whether you're building software or integrating services, mastering APIs is essential.

API Basics

How Requests and Responses Work

APIs operate on a request-response cycle to exchange data or perform actions. Here's how it works:

A client, like a mobile app or web browser, sends a request to an API server. This request usually includes:

Endpoint URL: The specific address for the resource or service.
HTTP Method: Such as GET, POST, PUT, or DELETE.
Headers: Contain details like authentication tokens or content type.
Request Body: The data payload, if needed.

Once the server receives the request, it:

Checks the authentication credentials.
Validates the provided data.
Executes the requested task.
Sends back a response.

The response includes an HTTP status code and, when applicable, the requested data. Now, let’s break down the key elements involved in these interactions.

Main API Elements

APIs rely on a few key components to structure their requests and responses:

HTTP Methods

GET: Fetches data.
POST: Creates new data.
PUT: Updates existing data.
DELETE: Removes data.

Status Codes
HTTP status codes are three-digit numbers that indicate the result of an API request [1]. Common examples include:

200 OK: The request was successful.
201 Created: A new resource was successfully created.
404 Not Found: The requested resource doesn't exist.

Headers and Body

Headers: Share metadata, like authentication tokens or the content type of the request.
Body: Contains the actual data being sent, typically formatted as JSON in RESTful APIs [2].

APIs for Beginners - How to use an API (Full Course / Tutorial)

How Requests and Responses Work

APIs operate on a request-response cycle to exchange data or perform actions. Here's how it works:

A client, like a mobile app or web browser, sends a request to an API server. This request usually includes:

Endpoint URL: The specific address for the resource or service.
HTTP Method: Such as GET, POST, PUT, or DELETE.
Headers: Contain details like authentication tokens or content type.
Request Body: The data payload, if needed.

Once the server receives the request, it:

Checks the authentication credentials.
Validates the provided data.
Executes the requested task.
Sends back a response.

The response includes an HTTP status code and, when applicable, the requested data. Now, let’s break down the key elements involved in these interactions.

Main API Elements

APIs rely on a few key components to structure their requests and responses:

HTTP Methods

GET: Fetches data.
POST: Creates new data.
PUT: Updates existing data.
DELETE: Removes data.

Status Codes
HTTP status codes are three-digit numbers that indicate the result of an API request [1]. Common examples include:

200 OK: The request was successful.
201 Created: A new resource was successfully created.
404 Not Found: The requested resource doesn't exist.

Headers and Body

Headers: Share metadata, like authentication tokens or the content type of the request.
Body: Contains the actual data being sent, typically formatted as JSON in RESTful APIs [2].

APIs for Beginners - How to use an API (Full Course / Tutorial)

How Requests and Responses Work

APIs operate on a request-response cycle to exchange data or perform actions. Here's how it works:

A client, like a mobile app or web browser, sends a request to an API server. This request usually includes:

Endpoint URL: The specific address for the resource or service.
HTTP Method: Such as GET, POST, PUT, or DELETE.
Headers: Contain details like authentication tokens or content type.
Request Body: The data payload, if needed.

Once the server receives the request, it:

Checks the authentication credentials.
Validates the provided data.
Executes the requested task.
Sends back a response.

The response includes an HTTP status code and, when applicable, the requested data. Now, let’s break down the key elements involved in these interactions.

Main API Elements

APIs rely on a few key components to structure their requests and responses:

HTTP Methods

GET: Fetches data.
POST: Creates new data.
PUT: Updates existing data.
DELETE: Removes data.

Status Codes
HTTP status codes are three-digit numbers that indicate the result of an API request [1]. Common examples include:

200 OK: The request was successful.
201 Created: A new resource was successfully created.
404 Not Found: The requested resource doesn't exist.

Headers and Body

Headers: Share metadata, like authentication tokens or the content type of the request.
Body: Contains the actual data being sent, typically formatted as JSON in RESTful APIs [2].

APIs for Beginners - How to use an API (Full Course / Tutorial)

Let's break down the key ideas behind designing and using APIs effectively.

API Endpoints

API endpoints are the specific URLs where resources or actions are accessed.

Each endpoint has two main components:

Base URL: The root address of the API.
Resource Path: The specific data or functionality being accessed.

For example, GitHub's API uses https://api.github.com/ as its base URL. To get a user's repositories, the path would be /users/{username}/repos [3]. Protecting these endpoints is crucial to avoid unauthorized access and misuse.

Security Methods

Securing APIs ensures that data and functionality remain protected. Some important techniques include:

Authentication: Confirms the identity of the user or system.
Authorization: Determines what actions a user or system is allowed to perform.
OAuth 2.0: Manages access using tokens.
Multi-Factor Authentication (MFA): Adds extra layers of verification for better security.

Usage Limits

Rate limits are used to control how often clients can interact with an API. This prevents overloading the system and ensures fair usage. For example, Twitter's standard search endpoint allows authenticated users to make up to 180 requests every 15 minutes [4].

To avoid hitting these limits, you can:

Cache responses to reduce unnecessary requests.
Use batching with exponential back-off to handle retries.
Monitor usage and set up alerts to identify potential issues early.

Let's break down the key ideas behind designing and using APIs effectively.

API Endpoints

API endpoints are the specific URLs where resources or actions are accessed.

Each endpoint has two main components:

Base URL: The root address of the API.
Resource Path: The specific data or functionality being accessed.

Security Methods

Securing APIs ensures that data and functionality remain protected. Some important techniques include:

Authentication: Confirms the identity of the user or system.
Authorization: Determines what actions a user or system is allowed to perform.
OAuth 2.0: Manages access using tokens.
Multi-Factor Authentication (MFA): Adds extra layers of verification for better security.

Usage Limits

To avoid hitting these limits, you can:

Cache responses to reduce unnecessary requests.
Use batching with exponential back-off to handle retries.
Monitor usage and set up alerts to identify potential issues early.

Let's break down the key ideas behind designing and using APIs effectively.

API Endpoints

API endpoints are the specific URLs where resources or actions are accessed.

Each endpoint has two main components:

Base URL: The root address of the API.
Resource Path: The specific data or functionality being accessed.

Security Methods

Securing APIs ensures that data and functionality remain protected. Some important techniques include:

Authentication: Confirms the identity of the user or system.
Authorization: Determines what actions a user or system is allowed to perform.
OAuth 2.0: Manages access using tokens.
Multi-Factor Authentication (MFA): Adds extra layers of verification for better security.

Usage Limits

To avoid hitting these limits, you can:

Cache responses to reduce unnecessary requests.
Use batching with exponential back-off to handle retries.
Monitor usage and set up alerts to identify potential issues early.

APIs streamline processes and help reduce errors. For instance, e-commerce APIs ensure inventory stays in sync across all sales channels, preventing overselling. In healthcare, APIs can automatically update provider calendars when patients book appointments.

APIs also play a key role in connecting platforms across industries. In financial services, where real-time data accuracy is critical, APIs automate tasks like transaction verification and updating account balances across banking systems [5].

Here are some tips for working with APIs effectively:

Store API keys securely: Use environment variables to keep your keys safe [6].
Double-check data accuracy: Compare results from multiple trusted sources to ensure reliability [6].

For communication, REST is ideal for standard request-response exchanges, while WebSocket is better suited for continuous real-time updates. To save development time, you can integrate pre-built services like Google Maps for location data or Facebook Login for authentication.

Next, we’ll look at how AI is transforming API testing.

Here are some tips for working with APIs effectively:

Store API keys securely: Use environment variables to keep your keys safe [6].
Double-check data accuracy: Compare results from multiple trusted sources to ensure reliability [6].

Next, we’ll look at how AI is transforming API testing.

Here are some tips for working with APIs effectively:

Store API keys securely: Use environment variables to keep your keys safe [6].
Double-check data accuracy: Compare results from multiple trusted sources to ensure reliability [6].

Next, we’ll look at how AI is transforming API testing.

APIs handle 80% of web traffic and are the backbone of modern apps in industries like healthcare, finance, and retail [11]. They define how software systems share data and interact, covering aspects like endpoints, security, and rate limits. As mentioned earlier, AI plays a key role in improving validation by automating testing, scanning for vulnerabilities, and identifying issues with precision [7].

Key factors for successful APIs include: