There are a lot of factors that go into the API comparisons. Some are backed by hard, undeniable fact. Others are more qualitative, but even those are usually based on some heuristic. Yet, when considering the great APIs, one thing rises above all these factors. There may be many things that great APIs have in common, but none are more important than continuous improvement.

I hesitate to use Twilio as an example, because it’s overdone in API circles. But I return to them because they have that one thing that great APIs have in common. When I’m talking with API providers, I don’t even have bring up Twilio, because they’ll almost list it along with a small handful of other APIs they aspire to emulate.

The new Twilio tutorials are an example of how an 800 pound gorilla can keep trying to get better. Already popular with developers for enabling them to get started quickly, Twilio saw an opportunity to help them build entire applications faster. The step by step tutorials bring focus to specific sections of code while allowing the developer to browse all the related files.

Another example from an API covered on this site is the new MapBox documentation. Already lauded for its beautiful site and helpful getting started guides, the mapping company found areas to improve, such as being mobile responsive and swapping languages on-the-fly. True to the company’s community focus, the whole thing is open source.

Whether leaders of mindshare or marketshare, great APIs remain that way by continually reaching for what’s better, often in an area where they’re already leading.

MapBox is going up against one of the largest companies in the world with a legitimate Google Maps alternative. Twilio comes from a more powerful position, but the SMS API comparison shows Twilio has plenty of competition, in quantity and in quality. They’re very different companies, at different stages. Yet, each continues to improve, making them both great APIs.