When working on a new project, developers typically want to move quickly. You need data and don’t want to wait to be approved for every API key. This is even more true when you’re just trying things out and experimenting with different APIs. Free public APIs offer a free solution to this dilemma.

Cost is just one reason to investigate free APIs, also referred to as public APIs or open APIs. They’re perfect for experimentation, for one thing. Open APIs can easily be linked together, as well, due to the openness of their data. If you’re looking to experiment with using multiple APIs in one project, public APIs are an easy choice.

Open APIs are also useful for building prototypes and mock-ups. If you’re demoing an app and need some real-time data, public APIs are an essential addition to your toolkit.

We’ve compiled a list of useful, fun, and interesting open APIs that you can use with no API key or authorization required.

1. 7Timer

Real-time weather data is helpful for a wide variety of applications. Maybe you want to build a simple weather app to sharpen your programming skills. Or perhaps you’re constructing a particularly advanced form of consumer analytics that cross-references customer decisions and weather conditions.

Or maybe you just want to know how cold it is outside.

Whatever you’re planning on using it for, 7timer will be welcome news. It’s a surprisingly robust, full-featured weather API that returns data on everything from humidity to cloud coverage to wind speed. Even better still, results can be returned in graphical and machine-readable formats.

2. Art Institute Of Chicago API

Museums and art galleries have been greatly missed during the pandemic. While most museums have re-opened in some capacity, we’re all still adjusting to this New Normal.

Of course, physical restrictions are just one reason that you might want a real-time source of high-quality art from across time and space. Art APIs offer an endless source of inspiration, if you’re struggling with a creative block, for instance. It’s also an invaluable resource for students of art and history.

The Art Institute Of Chicago is renowned for its world-class collection and traveling exhibitions. With the Art Institute Of Chicago API, you have that collection at your fingertips, at all times, available through numerous valuable endpoints.

The Art Institute’s website offers some examples of their API in action. Some have used it for everything from comparing one art collection to another while others have used it to create wall art for Animal Crossing.

Clearly, the Art Institute Of Chicago API isn’t just useful for killing time or overcoming creative hurdles. It’s perhaps even more useful for generating fun, interesting, and engaging programming inspiration!

3. Cat Facts

We all know that cats rule the internet. When it’s time to consume some APIs, it’s only logical to feed your program with data regarding our feline friends.

Then, it should come as little surprise to learn that there are numerous free cat APIs out there for experimentation. There’s Cat Facts which supplies you with interesting facts about family Felidae via HTTPS. Cataas does the same but with images and GIFs.

HTTPCat returns a different cat for different HTTP statuses, in case you want to make your 404s more fun. PlaceKitten does something similar but with random kittens for every occasion. RandomCats just rolls the dice, returning a random image of a cat. It’s far more fun than a random number generator!

4. Colormind API

We’re not all born with a perfect palette. It may take a keen sense to realize that pairing mustard yellow with ruby red might make you look like Ronald McDonald. This is just one of many reasons why web designers need to develop a good color palette. For instance, you might need to see what shades and hues might pair well with a light lilac. Or maybe you just want to know why some graphic is so incredibly enticing.

The Colormind API lets you generate color pallets from a provided image without having to open a website. This makes it suitable for automation, such as a UI generation project. Whether you’re looking to design a website, launch a brand or product, or just make your social media posts more appealing, Colormind will help with one simple curl command.

5. Currency-API

We live in a globalized world, which means we regularly do business with people from every corner of the globe. Even if our interests aren’t entirely commercial, there are so many different disciplines that require financial data.

Conversions seem like they should only require simple math, and they do — except for the fact that conversion rates are constantly fluctuating. And while there are a ton of different resources out there for converting one currency to another, many of them simply concert one country’s currency to another.

Consider Currency-API your Swiss Army currency converter. This humble API can convert over 150 different currencies, including popular cryptocurrencies. It’s updated daily and has no rate limiting or restrictions. Developer Fawax Ahmed is clearly doing the good work for Open Data!

6. Pixel Encounters

Are you ready to have a close encounter of the .svg kind? Maybe you’re trying to create your own spin on Space Invaders. Or perhaps you’re just tired of staring at blinking cursors all day.

Pixel Encounter is a fun, easy way to create random .svg sprites with a simple API call. This could be a fun addition for teaching kids how to code, perhaps. Or maybe you’re just looking for a simple touch to make your app or project slightly more exciting and unique!

7. Postman Echo

Sometimes you need to test an API. Sometimes you need a server to do that. Postman Echo is an open API that enables just that.

Developed by Postman, the API testing and development suite, Postman Echo allows you to send and receive GET, PUSH, and POST commands, each of which receives its own endpoint. It even incorporates various authorization techniques so that you can use it to test out secure APIs without any additional API keys or user tokens.

8. PurgoMalum

APIs are one of the most critical components of an automated system. They’re often the assembly line that powers bots and populates apps with content. If you’ve ever made, or even used, an automated bot to generate content, you know you never let a bot act without strict guidelines in place.

Enter PurgoMalum, an open API for detecting profanity and obscene material. Even better, it’s accessible with a simple HTTP request. All you have to do is send your content to https://www.purgomalum.com/service/xml as a query, and the results are returned as an XML file. Results can also be configured to be returned as a JSON file or even just a simple TRUE or FALSE response.

9. Random Facts API

Random facts are an easy way to ‘Hello World’ a new app or website. They’re an excellent resource for practicing programming or development, especially if they don’t require any kind of API key or API authorization.

The Random Facts API from Fungerators is particularly noteworthy as it doesn’t require ANY kind of authentication if you’re simply testing it out. You just have to navigate to their API endpoints, where you’ll see a wide array of endpoints for different applications.

If you’re looking to build a Fact Of The Day or Trivia app, you should give Fungerators’ APIs a look!

Free Public APIs: Final Thoughts

If you’re not careful, APIs can get expensive. Even $.0001 per API call can quickly balloon depending on what kind of traffic you’re dealing with.

At Nordic APIs, we’re also highly passionate about not having to spend a ton of money to learn or improve your programming. It’s probably the best thing about the internet, how there are so many powerful and useful resources available to everybody. Free, public, and open APIs are not only perfect for experimenting with APIs but are also powerful tools in their own regard, that won’t break your bank no matter how many times you call.