APIs are sets of definitions and protocols that allow software components to talk and interact with each other using a simple set of commands. Acting as messengers, APIs deliver one application’s request to another and return a response in real time.
If the server (the application providing the resource) can do what the client (the requesting application) asked, then the API will bring back the resource needed or a status code that roughly translates into mission accomplished! If the server can’t do what the client asked — maybe the client requested a resource that doesn’t exist or that it doesn’t have permission to access — then the API will return with an error message.
Controlling access to the server in this way is crucial. Rather than give you all of a program’s information or code, an API provides you only with data that has been made available to external users.
Why are APIs important?
If there were no APIs, the functionality of your applications would be limited, and the development time would increase significantly since any function that is not implemented as a module of one of the programming languages would have to be developed independently.
APIs tie disparate applications together, allowing them to complement each other.
If there were no API, each application would be limited to a narrow list of its own functions without the possibility of expanding it to something that others have already invented and used for a long time.
Benefits of APIs
APIs allow you to save time when developing and help not to invent a bicycle.
It is much more efficient and more convenient to use the capabilities of one of the APIs than to try to independently implement similar functionality.
APIs recharge your applications with the latest technology. With APIs, you can teach your application the latest image recognition and natural language processing methods.
API Calls
An API call is the process of a client application submitting a request to a server's API. An API call also comprises everything that happens after the request is submitted, including when the API retrieves information from the server and delivers it back to the client.
Request Methods
Most clients want the server to carry out basic functions. These requests may be written as URLs so that the communication between client and server is dictated by the rules of Hyper-Text Transfer Protocol (HTTP). The four most basic request methods to a server are:
- GET: To retrieve a resource
- POST: To create a new resource
- PUT: To edit or update an existing resource
- DELETE: To delete a resource
What is an API key?
An API key is a unique identifier used to authenticate calls to an API. The key is made up of a string of letters and numbers that identify the client (remember this is the application or site making the request). The key can grant or deny that request based on the client’s access permissions, and track the number of requests made for usage and billing purposes.
While not as secure as authentication tokens, this method has some advantages over basic authentication, which only requires a username and password.
By restricting access only to those with keys, a company can control the number of calls made to its API and ensure that only a specific, trusted group of clients can access its server’s resources.
Continuing our example above, think of an API key like a reservation and the API as an exclusive restaurant. By enforcing that patrons must have a reservation to eat at the restaurant, you can keep the number at capacity so that the kitchen can adequately and efficiently serve every guest. Similarly, by allowing only clients with an API key to access and use your resources made available via the API, you help ensure your software is used safely and can handle the number of requests coming in.