Application Programming Interfaces, or APIs, are intermediaries that relay communication between two programs in a format each respective application can interpret.
This allows owners to expose a part of the product’s functionality to third parties, all while keeping the rest of the application safe.
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As a marketer or content developer, this is a great chance to access the systems of major products and try to create new functionality. In this guide, we've compiled some of the best open APIs from the following categories:
- Marketing APIs.
- Website APIs.
- Email and Messaging APIs.
- Map APIs.
- News APIs.
- Image and Video APIs.
- Social Media APIs.
- Other open APIs.
However, because the proprietary organization needs to maintain a level of safety and management with the tool, there are certain limits to open APIs compared to other types of APIs. API management ensures the application remains at its best so all users enjoy the same benefits.
Publishing an open API might seem counterintuitive because of the security challenges. However, it can also effectively encourage innovation and make your product better suited for the market.
What makes a good open API?
Since open APIs are free to use and readily available to anyone, they’re not always going to be as polished as partner APIs (which are premium services). When browsing for open APIs to use, consider these criteria.
Documentation
No matter what API you’re working with, poor documentation is going to make you regret your choice. The best APIs, including those that are free, craft their documentation with care. These documents are also revisited and updated in a timely manner.
Always skim an API’s documentation before diving in.
Security
Open APIs should, at the very least, employ basic authentication and authorization methods. Usually, you’ll be given a free key to use when making API calls. This prevents your calls from being intercepted and transformed by malicious actors.
Simplicity
When it comes to the topic of APIs, “simple” is always a relative term. However, a good free API structures its resources clearly and logically for easy-to-understand requests.
Performance
Free APIs may place lower limits on the number of requests allowed within a given period. However, performance should not suffer simply because the API is public.
Slow API performance hurts user experience and may push users away from your app. If you can’t find a well-performing API that does what you want, you might have to invest in a paid API instead.
To make your life easier, we’ve rounded up the best free APIs you can use for your projects.
Free Marketing APIs
1. HubSpot API
With the HubSpot API, you can build custom solutions for your business’s marketing, sales, service, and website strategies. You’ll be able to add advanced functionality to an already powerful marketing software. Plus, you can integrate your HubSpot account with other tools.
2. Yahoo Search Marketing API
This free API lets you access Yahoo marketing data so you can better manage your marketing campaigns. Tailor your applications to display only the data you need with this well-documented solution.
3. Common Crawl
Crawling tools are effective because they can access internet data anonymously. This makes large amounts of data available for analysis and interpretation. Few can do it like Common Crawl, an API service that builds and maintains a repository of data accessible to all.
Free Website APIs
4. Google APIs
Google offers a wide range of open APIs that make it easier to work with Google’s many products. From Blogger, to AMP, to AdSense, to Maps, many Google services can be integrated via a specialized API.
5. WordPress APIs
The WordPress APIs are an ecosystem of tools that can extend WordPress capabilities. They are sorted into categories to help you to find what you need. Developers of plugins and themes will find this to be an especially useful resource.
6. Sejda PDF API
The Sejda PDF API allows you to integrate its PDF tools with your website and fill out PDF forms online. It also lets you streamline communication with others (such as vendors). You can automatically share signed documents or PDF forms they need to fill out.
Your customers can also copy your PDF templates easily.
7. QRcode Monkey
The QRcode Monkey API creates custom QR codes to add to your website or application. It’s accessible through RapidAPI.
Free Email APIs and Messaging APIs
8. Telegram API
Telegram is a messaging service with two APIs. The first is the Bot API, which lets you connect bots to Telegram — allowing you to use the messages as an interface. The second is an API that lets you build your own version of Telegram with full customization of the design.
9. Hunter API
The Hunter API allows you to find or verify the email addresses of professionals and companies. It can come in handy if you want to reach people whose contact information isn’t readily available online.
10. Mailchimp API
MailChimp has two APIs available for developers: a Marketing API and a Transactional API, along with a rich developer community to support them. Harness these resources to incorporate tailored email deliverability to your application.
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Everything you need to know about the history and use of APIs.
- A History of APIs
- Using APIs
- Understanding API Documentation
- And more!
Free Map APIs
11. Mapbox API
Mapbox is a leading provider of geolocation data for developers to build custom dynamic apps. It exposes its data through 10 different APIs for different uses. While primarily a paid service, Mapbox has a free plan that allows limited use of its APIs.
12. ArcGIS API
ArcGIS is powerful open-source software for mapping and data visualization. Its free API lets you create informative charts with geographic data displays. This includes both 2D and 3D map displays for impressive and professional-looking visuals.
13. Yelp API
With the Yelp API, you can access review data sorted geographically. You can then filter by ratings and distance from a location. You can use this to improve your local marketing efforts.
Free News APIs
14. The New York Times API
When you need to know what’s happening around the world, use a New York Times API. These APIs can pull any article, list, bestseller, tag, movie review, or other popular shared content for your project.
15. Associated Press API
When you need to know what’s happening around the world, use a New York Times API. These APIs can pull any article, list, bestseller, tag, movie review, or other popular shared content for your project.
16. News API
The powerful News API scans tens of thousands of news sources across the web. It then returns relevant content based on your request. This is a handy tool if you want to feature content relevant to your product or industry on your website.
Free Image and Video APIs
17. Shutterstock API
The Shutterstock API provides access to Shutterstock’s library. This allows you to search, view information, preview, license, and download media. This includes royalty-free images, music tracks, and video clips.
Use it to improve your site’s aesthetics and express your brand better with high-quality media.
18. YouTube API
This API helps you add YouTube functionality to your sites and apps. For example, you can use an embedded player in your app, enable users to subscribe in one click, and schedule and manage live broadcasts.
19. Vimeo API
Vimeo is a popular option for enterprise video hosting. Its API is a great choice when you want to add videos within your app and customize the playback experience. You can also take advantage of Vimeo's video tools.
Free Social Media APIs
20. LinkedIn API
With this API, you can add LinkedIn functionality to your sites and apps. That includes signing in, sharing on LinkedIn, integrating LinkedIn learning, and extending your marketing efforts to the platform.
21. Twitter API
The Twitter API helps you read and write Twitter data. This can help build scheduling apps and other productivity functionality. You can also find tweets containing certain keywords, hashtags, or topics.
22. Facebook API
Facebook offers a library of APIs and other developer resources. With this information, you can read and write data from Facebook, Instagram, Messenger, and WhatsApp. You can now monitor and write social media posts. This API can also manage your social media marketing activities.
23. Awe.sm
Awe.sm offers several APIs to integrate your social media marketing tools with your website or application. You can also track performance data.
Other Free REST APIs
24. Placekitten API
Who says work always has to be serious? Placekitten randomly generates amusing pictures of cute cats and kittens. You can use it to improve the mood around your website or simply put a smile on a colleague’s face.
25. APIMeme
Another fun API is the APIMeme. It lets you generate memes using a simple interface. With over 100 popular meme characters (like Condescending Wonka, Confession Bear, Confused Gandalf, Eminem, and Family Guy Brian), all that’s missing is a dose of your wit.
26. Spotify API
Does music play an important role on your website or application? Spotify’s open API allows developers to freely utilize Spotify song, album, artist, and playlist data. The API can also add songs to playlists and control music playback.
27. QuickChart
Use QuickChart to quickly generate chart and graph images that you can embed in email, chatbots, and SMS. It uses Chart.js, a robust open-source charting library. You can create a simple chart with a single URL. For more sophisticated charts, use the POST request.
28. Square API
Although all three are payment gateways, Square is unlike Stripe and PayPal. Rather than just letting customers send you payments, it lets you customize the payment gateway itself.
You can create gateways for your mobile app, website, and even your physical point-of-sale system. This improves the checkout process and user experience in general. Note that, while the API is free, Square charges a processing fee for all transactions.
29. IFTTT
IFTTT makes it possible to make your applications and devices work together by using simple “if this, then that” criteria. This means that one action is triggered by another as defined by you. For instance, you can set a photo or blog post to be shared across all platforms whenever it’s posted on one platform.
30. NASA
Through the NASA Open Data Portal, you can access NASA’s data on natural phenomena, both terrestrial and beyond. Particularly of use are its climate and weather data, as well as its visualizations.
Free Ebook: How to Use an API
Everything you need to know about the history and use of APIs.
- A History of APIs
- Using APIs
- Understanding API Documentation
- And more!
Getting Started
Our list includes some of the best free and open-source APIs for marketers and content developers. Use this list to improve your next project, campaign, blog post, or website.
Editor's note: This post was originally published in March 2020 and has been updated for comprehensiveness.
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