API is the way a developer can talk to another piece of software. Many applications have an API. 

An Application Programming Interface (API) is a computing interface that defines multiple software application interactions or mixed hardware-software intermediaries. It defines the types of requests that can be done, how to make these requests, the data format that should be used, the conventions to follow, and many more. APIS are also used to provide extension mechanisms so that users can extend existing functionality in different ways to different degrees.  

An API can either be custom, specific to a component, or created and designed based on an industry to ensure interoperability. By information hiding, API can enable modular programming which allows the users to use the interface independently of the implementation. 

API Applications

APIs are used for web applications like Google Drive, Gmail, Mailchimp, etc. But it can also be used offline like all of Microsoft Office applications.

Let’s take a closer look at the APIs used in Xero Accounting Software. 

The Xero API allows the developers to do such things as get a list of items you sell, get a list of your customers, create invoices for customers, create timesheets for your employees, and many more. 

If you need your application to “talk” to another service, you need to find the API. The quality of the API can vary greatly. Some API’s are very well thought out and easy to use. Others are not so easy to use.

Often they will have rate throttling so you can only make a certain number of calls in a time period, this is so Hackers cannot tie up all the resources of the service and deny other users access to the service. 

Usually the API will have some sort of key system such that you need to generate a unique key that is linked to your access to the service. The developer needs to put that into the software so they can send this to the service and the service knows we are happy to talk to our data.

API Documentation

A good API will have excellent documentation. Some API’s work better with certain programming languages better than others. For example some API’s made with the .NET Framework don’t play well with anything other than languages on the .NET Framework.

Types of API

APIs, just like any other language, come in different forms. API developers and designers can choose from a lot of standards and protocols when designing a new API. It depends on a lot of things, but mainly, they are based on its purpose. 


This type of APIs can be accessed using the HTTP protocol which all the Web Works on. It defines the valid requests and response formats, as well as the end points. Web APIs are the APIs used to communicate with the browser. It can also include services like web storage and web notifications. There are different features of web APIs depending on the levels of security and privacy like internal, open, and partner APIs. 

Internal APIs

This type of API is designed to be hidden from public and external users. These are just used within an organization and are specifically designed for a company. 

Open APIs

Open APIs are known as public or external API. They are available to developers and other users with little restrictions. These APIs usually require registration and use of an API key, but can also be completely open.

Partner APIs

Partner APIs are somewhat similar to open APIs but they use a third-party API getaway to feature restricted access. These APIs are often intended for a main specific purpose like giving access to a paid service. 

Composite APIs

Composite APIs give developers access to several endpoints in one call. It can be various endpoints in one API or different endpoints in multiple data sources or services.

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