39 Must-Have APIs for Developers

If you want to build your own tools off of the functionality of an existing application, you need an API (Application Programming Interface). Whether you need to create synergy among your company’s software applications or create an entirely new application that taps into the functionality of a mainstream platform, APIs are pretty much essential to the development world. So much so that the majority of widely used applications now issue APIs as a standard–allowing their apps to be integrated with other commonly used applications, CRMs and the other tools that enterprises rely on.

The following 40 APIs are handy to have in your developer toolkit. Whether you want to integrate social media advertising with your company’s CRM, automate processes, or develop a new platform that works in conjunction with a popular e-commerce platform, there’s an API to meet your needs.

Image via Flickr by Risager

1. Facebook APIs
Facebook provides a set of APIs with functions ranging from integrating chat to querying data exposed by the Graph API using an SQL-style interface. The Facebook Ads API allows you to create your own applications instead of using the Facebook Ads Manager or Power Editor tools.

Key Features: 

  • Integrate chat, Graph, dialogue, and other features into your own customized apps
  • FQL (Facebook Query Language) to integrate advanced features based on other queries not available with the Graph API
  • Build your own Facebook ad management and editing platforms with the Ad API

2. Twitter
Twitter’s API allows developers to use Twitter Cards to accomplish more with just 140 characters–including allowing Twitter to get more insights into shared URLs and drive more traffic to your website or application. The API also allows for such functionality as embedded Tweets, embedded timelines, and Tweet and Follow buttons.

Key Features: 

  • Embed Timelines or Tweets
  • Use Twitter Cards for enhanced functionality
  • Get more traffic to your site or app through advanced analytics
  • Integrate Tweet and Follow buttons

3. YouTube
YouTube offers a Data API, Analytics API and Livestreaming API for integrating a variety of YouTube functionality into your applications. Use the YouTube APIs to grab search results and retrieve, insert, update and delete playlists, videos and other resources. When used in conjunction with each other, YouTube’s set of APIs allow you to create a fully functional YouTube experience from within your own applications.

Key Features: 

  •  Combine 3 APIs for full YouTube functionality integration
  • Build in search and discover, create content, and playback videos
  • Analytics integration and account management

4. Google 
Google offers a slew of different APIs for developers to integrate the functionality of the many Google properties into their own development projects. From Blogger to Analytics and Ad Exchange Buyer and Seller APIs, the possibilities are pretty much endless.

Key Features: 

  • APIs for practically every Google application
  • Integrate ad management
  • Use the AdSense API to build in publisher access to inventory and enable report generation
  • API console for monitoring API usage and access control
  • Google Developers resource with full API information and tutorials

5. HootSuite

HootSuite’s Engagement API provides access to HootSuite’s core social media management and message publishing functionality. Build in the capabilities of HootSuite to add comprehensive social media management to your applications.

Key Features: 

  • Supports OAuth 2.0
  • Draft, schedule and publish from any data source
  • Organize social networking teams
  • Manage the HootSuite web dashboard configuration

6. Yelp
Access Yelp data from any application in real-time with Yelp’s API. Pull business listing info, review counts, ratings and more with full API integration.

Key Features: 

  • Registration provides instant access to 10,000 API calls per day to build your prototype
  • Increase call limits for public launch by submitting a link to and screenshots of your prototype
  • Access Yelp data in real time
  • Business listing info, ratings and review counts, deals and recent review excerpts

7. Oodle
A full-featured REST-based web service, Oodle’s API provides access to access to “the same listings and search engine that Oodle uses to power Walmart, MySpace, and Oodle.com.”

Key Features: 

  • Read-only; API allows you to retrieve, but not insert listings
  • Integrate classified listings into your website or application
  • REST-based web service

8. Yahoo!

While the Yahoo! Local API is scheduled to be shut down as of September 28, 2013, Yahoo! still offers a number of APIs you should stash in your toolkit.  With Yahoo! Query Language (YQL), you can call and integrate data from multiple web services to run your apps faster and with fewer lines of code.

Key Features: 

  • YQL to query, filter, and join data across Web services
  • Flickr API for both image viewing and uploading access
  • Yahoo! BOSS Geo Services to integrate location-based data

9. Open Street Map
Open Street Map’s Editing API isn’t designed for embedding maps into a web page. There’s a different app for that. Instead, the Open Street Map Editing API lets you fetch and save raw data from the Open Street Map database. It’s intended for the purpose of editing map data, not for read-only projects.

Key Features: 

  • Editing API for fetching raw data
  • Not for read-only projects
  • Edit map data from within your applications

10. Instagram
Instagram wants its users to have open access to their data–thus the Instagram API, allowing developers to make use of the rich content uploaded to the platform every second in unique and innovative ways.

Key Features: 

  • Each application has its own assigned OAuth client ID and client secret
  • Developers must respect user Copyrights
  • Apps must not replicate the Instagram experience or use the Instagram name

11. WordPress

WordPress offers a set of APIs for replicating and integrating the plugin/theme/add-on interface of the WordPress dashboard. From a Dashboard Widgets API to Theme Customization API and Metadata API, you can incorporate a variety of WordPress functions into your applications.

Key Features: 

  • WordPress.com and WordPress.org APIs
  • Ideal for plugin or theme authors
  • Customize admin screens
  • Add your own custom widgets
  • Developer portal for discussions and tips

12. Ning
Ning’s API allows you to create custom mobile apps, desktop applications, develop content importers for third-party blogging platforms and more. With a full set of developer docs for reference, there are endless possibilities for integrating Ning’s features into your custom applications.

Key Features: 

  • Build a custom Ning Network feature
  • Create custom apps for the Ning community to install on personal profile pages
  • Integrate desktop activity network monitors, media editing applications and more
  • Create mobile apps for any OS

13. Klout

Klout’s API offers the functionality for so much more than merely displaying Klout Scores and data. Pairing the Klout API with other APIs from Twitter, Viggle, Spotify and other prominent platforms creates opportunities for a totally customized app capitalizing on the advanced features of several networks.

Key Features: 

  • Ideal for pairing with other APIs
  • KloutPass – an OAuth API that lends you the Klout brand to deliver a VIP experience to influencers
  • Leverage the Influence Graph
  • Perfect for performance measurement and analytics
  • User-based API

14. Social Mention
Interact with the Social Mention website programmatically with the Social Mention API. “The API provides a single stream of real-time search data aggregated from numerous social media properties.”

Key Features:

  • Aggregate data from multiple social networks into a single stream
  •  An API call initializes live querying of each social media source and the data is sorted, processed, and normalized
  • Results are limited to the most recent items from each source (data is currently not archived)
  • Varying data limits set by each social network

15. Reddit
Reddit’s API and code are open-source, so it’s subject to change as various developers weigh in with added functionality. The Reddit API enables you to retrieve and display data from the Reddit website. This REST-based API returns data in JSON and requires no authentication.

Key Features: 

  • REST-based API
  • Open-source
  • Retrieve and display Reddit data up to 100 links
  • No authentication required
  • Data returned in JSON format

16. Bit.ly

Bit.ly’s URL shortening service offers APIs for link analysis, real-time search and more. The APIs enable both specific phrase queries and filtering data, as well as the ability to get an overview of trending topics across all social networks. Bit.ly’s Social Data APIs exited Beta in January 2013.

Key Features: 

  • True, real-time search for specific queries and filtering data
  • Return current phrases getting the most attention with the Bit.ly bursts API
  • Realtime story pages aggregate trending articles into a single source
  • Query on a URL basis for keywords, topics, content, language, and location relevance

17. Opus Social Media API 
The Opus Social Media API is “a hosted social media API for developers and creative agencies.” The Social Media API enables developers to build fully functional, rich social media applications without reinventing the wheel.

Key Features: 

  • Supports both REST and SOAP web services
  • JSON, JSONP and XML output formats
  • 150ms average response time
  • 99.9% uptime since 2003
  • Manage and publish digital media (professional and UGC video, audio, images and documents)
  • UGC moderation tools
  • Analytics and reporting tools

18. Awe.sm 
The Awe.sm API is used for integrating social media campaign tracking tools into an app or website. Power sharing features, understand social behavior and increase value from every share. 

Key Features: 

  • Account required; pricing starts at $19 per month
  • Conversion tracking and other analytics
  • Awe.sm links represent a sharing action, not just a long URL
  • Each share has a unique link per network for performance measurement

19. AppAware

The AppAware API enables the embedding of AppAware profiles in your website or application, access Google Play apps and more.

Key Features: 

  • OAuth 2.0 compatible
  • Based on the android-market-api library
  • Quickly access details of Google Play apps

20. Strands Recommender
Strands Recommender is an easy-to-use social recommendation and personalization platform offering an API for user management, recommendation integration and other functions.

Key Features: 

  • Automated cross- and up-sell recommendations based on user behavior
  • Email recommendations and targeted campaigns
  • Both product-based and user-based reporting capabilities
  • A/B testing, algorithm controls and merchant-defined promotions, rules and filters

21. alternativeTo 
alternativeTo’s API returns queries including information about the specified application as well as the user-specified number of alternatives. Alternatively, results can be returned and filtered by the applications a specified user has liked or recommended.

Key Features: 

  • Filter by license or platform
  • Find alternatives to applications
  • Search by user-generated recommendations or additions

22. CloudMade

CloudMade offers APIs for Map Tiles, Geocoding and Routing for enhancing your applications with real-time, turn-by-turn navigational capabilities and more.

Key Features: 

  • 99.9% uptime or 2x money back
  • Real-time, turn-by-turn routing
  • Forward and reverse geocoding
  • Thousands of categories
  • Pricing based on API and use limits:
    • Map Tiles: $25 per 1 million tiles; first 500,000 tiles free
    • Geocoding: $15 per 100,000 requests; SSL for $5 per 100,000 requests
    • Routing: $15 per 100,000 requests; SSL for $5 per 100,000 requests

23. MapQuest
MapQuest’s iOS and Android maps APIs are designed as drop-in replacements for the native API, with enhanced features such as integrated driving directions and the ability to use OpenStreetMaps data and MapQuest’s licensed data sets.

Key Features: 

  • Multiple APIs, including Free Map, iOS, Android and Native Mobile Mapping 
  • Licensed and Open Data available
  • No pre-set limits on maps with the free Community Edition license

24. Intigi
Intigi’s API allows you to streamline content marketing efforts with targeted user groups, as well as increase site traffic. Put your customers in touch with user-generated sources.

Key Features: 

  • More than 30,000 user-curated sources
  • Monitor a variety of online information sources (blogs, social networks, news wikis, etc.)
  • REST-based architecture (JSON via HTTPS output format)
  • Filter the best and most relevant sources for display or to connect application users

25. Parse.ly

Built specifically for online content publishers, the Parse.ly API helps you better engage users with content.

Key Features: 

  • Uses natural language processing technology 
  • Analyze reader behavior and content engagement to expose trends
  • Parse.ly Dash provides exposes data analytics in real-time

26. Animoto
Animoto’s API “is a web service that transforms pictures, music, video clips, and text into professional-caliber videos.”

Key Features: 

  • Multiple opportunities to create rich video experiences
  • Generate video creation experiences within your app
  • Auto-render videos in bulk
  • Various programming languages
  • JSON and XML support through RESTful HTTP
  • Ruby and Java built-in client libraries
  • Access to commercially licensed song lists

27. SendGrid Analytics
SendGrid Analytics offers an API enabling users to obtain data from their SendGrid accounts, such as statistics, spam reports, unsubscribes and other data. Customers may also create sub-accounts and control settings with an OEM setup. SendGrid also integrates with Embarke

Key Features: 

  • Obtain real-time hooks on bounces, clicks, unsubscribes and more
  • Send multiple emails
  • Customize plugins
  • Manage subscriptions for resellers and subusers

28. Embarke
Embarke is a development tool for social communications with back-end conversation capabilities. Embarke’s API is used to expose data from six variables, including users, networks,  accounts, conversations and messages.

Key Features:

  • Expose data from six critical sources
  • One API to connect to multiple social networks
  • Create a social CRM app, enable users to share photos, create an app for group conversations and more

29. CrunchBase
The CrunchBase API “provides a RESTful interface to the data found on CrunchBase” with JSON output format. The CrunchBase API was introduced in 2008 and has been used to enhance a variety of applications, such as WordPress plugins and social graphs.

Key Features: 

  • Retrieve and aggregate data from a variety of industries
  • Multiple search-based and filter queries possible
  • Custom parameters possible for retrieving different data sets

30. Agile Bench
Agile Bench is a project management tool that integrates flawlessly with a variety of applications, including GitHub, Pivotal Tracker and more. The API exposes five resources, including token, project, iteration, story and comment.

Key Features: 

  • JSON payload format
  • HTTP codes explain status
  • User authentication via tokens

31. Agile Zen
Agile Zen’s API is still in Beta, so it’s subject to change. Currently, resources are organized into two primary types: entity resources and container resources. Resources include comments, tasks, stories, comments, projects and more.

Key Features:

  • REST-based
  • Retrieve data on stories, projects, comments and more
  • Integrate project management capabilities into any application

32. Bug.ly
Bug.ly is “a modern, flexible and enjoyable issue tracker with a powerful REST API, excellent SCM integration, issue dependencies, custom statuses, email integration and much more.”

Key Features:

  •  Supports JSON
  • Simple resource-based structure
  • Comprehensive documentation
  • Ruby library

33. LeadSyncer

LeadSyncer’s REST-based API returns JSON-based records, allowing you to feed generated leads directly into a third-party or custom-built CRM/ERP system.

Key Features:

  • Simple HTTP GET calls
  • REST-based
  • JSON format
  • View transmitted records in a browser
  • Easy URL-based record retrieval
  • Design your own data forms
  • Export leads into Excel
  • Automatic syncing with an Internet connection; some offline functionality

34. Amazon Product Advertising API
Critical for any developer wanting to monetize a website or app, the Amazon Product Advertising API integrates Amazon Product Listing Ads within an app and provides programmatic access to Amazon’s product selection and discovery functionality.

Key Features: 

  • Ideal for monetizing apps and websites
  • Integrate Amazon’s product selection and discovery functions
  • Advertise products in conjunction with Amazon Associates program

35. Highwire
Highwire offers both an HTML and REST-based API, enabling both the retrieval and modification of store records such as orders, products, customers and categories.

Key Features:

  •  Retrieve and modify categories, customers, orders and products as required
  •  Accepts and responds with XML or JSON-formatted data
  •  Limited to making a maximum of 500 calls for each individual store (rolling every 5 minutes)

36. IconFinder

IconFinder’s API integrates icon-search functions into your websites and applications.

Key Features: 

  • Search for icons via search terms
  • Multiple parameters, such as result page, icons per page, etc.

37. PayPal 
“PayPal offers a set of application programming interfaces (APIs) that give you the means to incorporate PayPal functionality into your website applications and mobile apps.”

Key Features: 

  • Both Sandbox and Production environments
  • Both SOAP and non-SOAP request and response formats
  • x-www-form-urlencoded, XML-RPC, and JSON-RPC non-SOAP formatting options

38. Constant Contact
Constant Contact’s API is used to both integrate contacts and send and receive email marketing campaigns within third-party applications.

Key Features: 

  • Integration-specific on-boarding and educational resources
  • Revenue share options as high as 40 percent per month
  • REST, JSON, and OAuth 2.0 compatible
  • iOS, C# and other development libraries

39. MailChimp

MailChimp’s API allows you to integrate functions with a CMS, blog, shopping cart, and more.

Key Features: 

  • OAuth2 handles usernames and passwords so you don’t have to
  • Export API allows you to stream large amounts of data
  • Webhooks to collect data in real-time

What APIs do you keep stashed in your developer’s toolkit?  Which one of these does your application use the most? Share them with us.