You’ve probably used PayPal to pay for something you ordered through Amazon. Or perhaps logged into a mobile game using your Facebook account. Or simply checked Google Maps for directions directly in the Uber app.
Without APIs, or Application Programming Interfaces, all of these scenarios wouldn’t be possible. Why? Because APIs connect different apps together, so they can communicate and exchange information.
In this article, I will explain the basic concept of API, common API terms you should know, and finally, how to get started with API.
What is an API?
An API is a set of rules and protocols that facilitate communication and data transfer between different software systems and apps. As a result, these apps can work seamlessly to serve your request.
When you order groceries via Uber Eats, you might think that you’re only using one app, right? But in reality, there are hundreds of apps running in the backend. Each communicate through APIs to make your order happen.
The Uber Eats app might use the Google Map API to track your current location, connect with the Apple Pay API to process your payment, and integrate with a review app to handle the review you’ll leave at the end of each booking.
Why do we need APIs?
Without APIs, it would be impossible for us to enjoy the convenience of modern apps. You won’t be able to sign up to a new website using your Google account, sync your phone's images with Instagram, and navigate your way to the nearest Starbucks.
APIs make it easy for software engineers and developers to build apps with many functionalities without actually reinventing the wheel. For example, Uber can simply integrate Google Map into their app to provide location tracking without developing their own map system.
SaaS providers like Boltic also leverage the power of APIs to connect hundreds of popular apps into one integrated system, so you can automate your entire workflow and sync data across different platforms.
Key API terms you should know
Before you can understand how to use an API, you’ll need to get familiar with all the technical API terms first:
API client
An API client is a user-facing app, program, or tool you can use to connect with an API. It could be your computer’s own command line app, or third-party tools like Postman and Insomnia.
API request
An API request is a message sent by a client to an API server. It basically tells the API to do something you want, like retrieving information. To make an API request, you can use four methods:
- GET – for retrieving information from an API
- POST – for adding new data to a server
- PUT – for updating records on an API
- DELETE – for removing existing data on a server
Many public APIs allow GET requests without authentication, while other methods like POST, PUT, and DELETE typically require proper authentication.
API response
After you send a request to an API server via a client, the server will then come back with an API response. It usually tells you whether your request is successfully completed or not via a status code.
Status code
A status code tells you the current status of your request. Is the request successfully completed? If not, what went wrong?
Common status codes include:
- 2XX – the server understands your request and is processing it
- 3XX – the server understands your request, but the data has been moved or deleted
- 4XX – the server can’t understand your request because something is wrong with it; maybe the request is too large or missing some credentials
- 5XX – the server experiences an error, so it can’t process your request
API key
An API key is some sort of a password you’ll need to access APIs. It’s an authentication method to make sure that only authorized users can retrieve the data within the API. Beyond an API key, many APIs also use OAuth 2.0 and JWT as their authentication methods.
API server
An API server hosts the API of a specific app or service. For example, if you wanna add a mapping system to your app, you'll have to send an API request to the Google Maps API server.
API call
An API call is the process that occurs when a client sends a request to an API server, and receives a response.
Endpoint
An API endpoint is a specific URL path on the API server that corresponds to a particular function or resource. A common example of API endpoints is the login page of a website. Here, you’ll find different endpoints or buttons that trigger different actions. There's one for creating a new account, another one for logging in using your credentials, and the last one for resetting your forgotten password.
Parameters
API parameters are the specific details of an API request. For example, if you want to retrieve information about electronic products only, you can add the “category=electronics” query parameter to the API endpoint.
Rate limiting
Rate limiting is a technique for restricting the number of API requests that can be made within a given timeframe. It prevents API clients (which can be malicious actors) from sending too many requests to an API server, which could lead to errors and crashes.
Error handling
If an API request comes back with a 4XX or 5XX status code, it means something is wrong. Error handling is basically the mechanism or strategy you implement to deal with those error codes. Examples include re-checking your request (is there any typo?), re-trying the request, or notifying your development team so they can take a look.
Types of APIs
There are two ways to categorize APIs, either by the communication protocol or the accessibility level (a.k.a which users have access to the API). In terms of the protocol used, there are 3 forms of APIs:
- SOAP API – uses XML (extensible markup language) to structure API requests and supports advanced security features like WS-Security, making it suitable for sensitive data exchange.
- Rest API – uses HTTP (hypertext transfer protocol) to send requests to an API server and retrieve specific data or perform actions on resources. Its web-based nature offers more flexibility and scalability than SOAP. So, no wonder it's the most popular form of API today.
- GraphQL API – unlike REST, uses a single endpoint and allows clients to specify exactly what data they need. It’s gaining traction for its ability to minimize network requests, which often lead to faster app performance.
Based on their accessibility level, APIs can be grouped into several categories:
- Open API – like the name implies, it's accessible by the general public. Examples include the Google Maps API, the Slack API, and the HubSpot API.
- Internal API – only users in certain companies can use an internal API to share private data or sensitive information.
- Partner API – a form of API that exposes a company’s data or services to external partners. Think about Amazon's Product Advertising API, which is accessible only by registered developers.
There's also a composite API, which allows you to integrate with multiple backend services in a single API call.
API versioning and deprecation
APIs don't stay the same. As companies add new features or roll out new updates to their app, the API also has to be modified to reflect those changes. The problem is, even the smallest change to an API can break existing connections with third-party services.
This is why you need API versioning. It lets developers introduce new versions of their API without forcing all integrated apps to update immediately. External tools can continue using the older API version while gradually migrating to the new one at their own pace.
Here's an example of API versioning:
- https://api.example.com/v1/paypal
- https://api.example.com/v2/paypal
As you can see here, /v1/ and /v2/ represent different versions of the PayPal API. If, for some reason, PayPal decides to retire the v1 version, the process is called deprecation. When API is deprecated, it will still be available for a certain period. But new features won't be added, and developers are encouraged to migrate to the latest version.
How to use an API
By now, you've pretty much understood the basic concept of API. Next, let’s talk about how to actually use an API.
1. Read the API documentation
Each app builds their API a bit differently. So if you want to interact with an app, you’ll have to read its API documentation to know:
- The endpoint (URL) where you can access the API
- The exact format to follow when writing an API request
- What you can do with the API
You can find public APIs on directories like RapidAPI or API List, or by exploring GitHub repositories of open-source projects. Already have a certain app in mind? You can simply visit its website and head to the "Developers" page to locate the API documentation.
2. Select an API client
You need an API client to be able to send requests to an API server. Some of the most popular API clients include:
- Postman – an easy-to-use tool for submitting and evaluating API requests.
- cURL – an open-source command line tool for HTTP data transfers.
- Insomnia –a desktop app used to design, test, and debug RESTful APIs.
3. Obtain your API key
An API key ensures the security of your API connection. That's why, you must obtain an application's API key (which is typically mentioned in the API documentation) before connecting to it.
Once you have your API key, you'll need to include it in every API request you send. The API documentation usually tells you exactly where this key should go – typically in a request header. If you’re using Postman, you can input these credentials in the “Headers” tab.
4. Write your API request
Here comes the exciting part: sending your first ever API request! You still remember about the common request methods I told you before, right? If not, let me remind you quickly:
- GET for retrieving data
- POST for adding data
- PUT for updating data
- DELETE for removing data
Depending on the client you use, the precise procedures for submitting an API request may vary. For this tutorial, I'll show you how to send a GET request to the Google Drive API using Postman:
- Once you create an account, access the dashboard and select Send an API request.
- From the dropdown menu, choose the request method (in this case, GET).
- Fill in your GET request in the provided field. Here’s an example:
GET "https://www.googleapis.com/drive/v3/filename"
- Enter the Google Drive API key in the Headers tab.
- Click Send to submit your API request.
That's it. If your request is successful, the tool will show the ‘200 OK’ response code along with all the data you requested.
Connect your apps without dealing with APIs
If setting up an API connection manually seems too complicated, you can always use a no-code tool like Boltic. All you have to do is create a free account and start integrating all your favorite apps in a single, centralized system.
We've made it simple for you to automate your entire business process, from updating inventory whenever a transaction is made, to syncing customer data across your accounting and CRM platforms.
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