Have you ever been stumped how to design a Web API? There are so many different approaches that you can take for even simple things, like paginating API result sets. If you list out your options, it can be easy to end up in analysis paralysis.

I like to remind myself that I’m not the first person to tread on this soil. I often take inspiration on design choices from well-known APIs, assuming that the hard work has already been done. But I realized lately that I’m not confident what a popular or successful API is, and that I have my own exposure biases in what is popular or successful. So, I decided to do some research to address that.

I defined an API’s success and popularity based upon whether it is supported by integration solutions. Integration solutions are systems which allow for the easier connecting or APIs together. I figure that if a service or API is popular, customers will demand it be available in integration systems that they use. As a result, the supported APIs could be correlated to determine the most popular APIs for integrating with.

I gathered the available APIs in nine integration platforms: Zapier, Mule ESB, ifttt, itDuzzit, Pipethru, Formstack, Magic xpi, Adeptia, and CloudWork. These platforms cover a range from being Startup-y to Enterprise-y.

So, here it is; the most popular APIs by their integration platform support:

API Integrations Integration Solutions
Dropbox 7 Zapier, ifttt, Mule, itDuzzit, Pipethru, Formstack, CloudWork
Google Calendar 7 Zapier, ifttt, Mule, itDuzzit, Pipethru, Formstack, CloudWork
Salesforce 7 Zapier, Mule, itDuzzit, Formstack, Magic-xpi, Adeptia, CloudWork
Twitter 7 Zapier, ifttt, Mule, itDuzzit, Pipethru, Formstack, CloudWork
Box 5 Zapier, ifttt, Mule, itDuzzit, Formstack
Facebook 5 Zapier, ifttt, Mule, itDuzzit, Pipethru
Gmail 5 Zapier, ifttt, itDuzzit, Pipethru, CloudWork
Google Contacts 5 Zapier, Mule, itDuzzit, Formstack, CloudWork
WordPress 5 Zapier, ifttt, itDuzzit, Formstack, CloudWork
Campaign Monitor 4 Zapier, itDuzzit, Formstack, CloudWork
Chargify 4 Zapier, itDuzzit, Formstack, CloudWork
Evernote 4 Zapier, ifttt, Pipethru, CloudWork
FreshBooks 4 Zapier, itDuzzit, Formstack, CloudWork
Google Drive 4 Zapier, ifttt, itDuzzit, CloudWork
Highrise 4 Zapier, itDuzzit, Formstack, CloudWork
LinkedIn 4 Zapier, ifttt, Mule, itDuzzit
NetSuite 4 Zapier, Mule, itDuzzit, Adeptia
Quickbooks 4 Zapier, Mule, itDuzzit, CloudWork
Stripe 4 Zapier, itDuzzit, Pipethru, Formstack
Toggl 4 Zapier, itDuzzit, Pipethru, CloudWork
Trello 4 Zapier, itDuzzit, Pipethru, CloudWork
Yammer 4 Zapier, ifttt, Mule, itDuzzit
Zendesk 4 Zapier, itDuzzit, Formstack, CloudWork
ActiveCampaign 3 Zapier, itDuzzit, CloudWork
Asana 3 Zapier, itDuzzit, CloudWork
Authorize.Net 3 Zapier, Mule, Formstack
Basecamp 3 Zapier, itDuzzit, CloudWork
Batchbook 3 Zapier, itDuzzit, Formstack
Blogger 3 ifttt, Mule, itDuzzit
Campfire 3 Zapier, ifttt, itDuzzit
Capsule CRM 3 Zapier, itDuzzit, CloudWork
Chatter 3 Zapier, ifttt, itDuzzit
Constant Contact 3 Zapier, itDuzzit, Formstack
Desk.com 3 Zapier, itDuzzit, CloudWork
Flickr 3 ifttt, Mule, itDuzzit
FreeAgent 3 Zapier, itDuzzit, Pipethru
GitHub 3 Zapier, Mule, itDuzzit
Google Docs 3 Zapier, itDuzzit, Formstack
Google Talk 3 Zapier, ifttt, itDuzzit
Google Tasks 3 Zapier, Mule, itDuzzit
JIRA 3 Zapier, Mule, itDuzzit
MailChimp 3 Zapier, itDuzzit, Formstack
Microsoft Dynamics CRM 3 Zapier, itDuzzit, Magic-xpi
PayPal 3 Zapier, Mule, Formstack
SugarCRM 3 Zapier, Mule, CloudWork
Twilio 3 Zapier, Mule, itDuzzit
WebMerge 3 Zapier, itDuzzit, Formstack
Zoho CRM 3 Zapier, itDuzzit, CloudWork

RSS, SMS, and e-mail also get a nod at being well-supported by these integration platforms, but I excluded these from this list as they don’t fit in as APIs that you can look at and learn from.

Join in the discussion over at reddit and Hacker News.