Applications You Can Build with Free APIs

With free APIs, developers can practice programming by using those APIs to create applications. Once you have practiced writing apps, you can then move on to paying for some APIs that you can use to write even more useful or complex apps.

Phone Number Validator

There is a multitude of free APIs that are available to the public. So, your options for the types of APIs you can practice with are almost endless. One such API you can use to build applications is a phone number validator API, which enables you to ensure telephone numbers are valid for hundreds of countries around the world. With a phone number validator API, you can also find the company associated with a number and its location.


The big Git hosts, like GitHub, Gitlab, and Bitbucket, all provide their own APIs to enable developers to automate tasks like pulling and pushing code and merging code. Authentication is provided via OAuth, so you can be sure the APIs are secure and authentic.

Validation APIs

With APIs like Let’s Validate, you can discover what technologies are being used on other websites. You can use validation APIs to reveal the technologies that are of interest. And because there is no authentication required, you can begin using the data straight away.

API Testing

APIs like the Postman API enable you to make requests easily. You can write programs to script the testing of APIs. You can also send query strings and headers, and get response headers and bodies. If you are building an application, APIs used for testing are essential.

Website and RSS Aggregator

With this type of free API, you can aggregate data from a multitude of websites and RSS feeds and put them all in one place. Website and RSS aggregator APIs support CORS, which means you can access data straight from frontend apps. The aggregated information is returned in JSON format, so you are able to use the data immediately. You can use it to crawl websites, and RSS feeds to extract whatever data you want.

Dictionary APIs

Various free public APIs enable you to create your own dictionary application. Popular ones like Oxford Dictionary API and Merriam-Webster API are free as long as you limit your queries and sign up for an API key to access them. Dictionary APIs provide definitions of words and pronunciations. They often also include things like a word-translator and thesaurus. You can use sentences APIs to gain example sentences that contain given words, as well.

File Conversion APIs

File conversion APIs convert data between different formats, such as HTML, image files, and Office files. Other data formats you can convert include XML to JSON and CSV to JSON. You can also use file conversion APIs to merge multiple Office files into one document. Furthermore, you can use email validation APIs, barcode scanning APIs, OCR APIs, and natural language processing APIs for file conversions too.

Other Free APIs

In addition to those mentioned above, there is a plethora of other APIs that you can use to build applications. Some of the best free public APIs include:

·       SYSTRAN Platform, which allows you to utilize and analyze both structured and unstructured content, such as social media and web content, in multiple languages.

·       Open Weather Map, which enables you to receive weather data from any location on the planet.

·       Investors Exchange Trading, which returns a wide range of effective spread, eligible volume, and price improvement of any stock, by each individual market.