Since quitting Tumblr, his main project has been Instapaper, the killer "read it later" iPhone and iPad app so beloved by New Yorkers who ride the subway. There's a free version and a paid version, and you can guess which one has been downloaded more—despite the fact that "Instapaper has nontrivial operating costs," in the words of Mr. Arment, and he's at least partly dependent on the revenues.

In order to encourage more people to subscribe, Mr. Arment limited support for third-party developers making apps that work with Instapaper. He allowed developers to make Instapaper apps with simple functionality via a restricted A.P.I. But the restrictions led to a rash of buggy, crashy apps that got around the limitations of the official A.P.I. by scraping the Instapaper website.

So yesterday Mr. Arment announced a clever solution: a full A.P.I. that will only work for customers who are Instapaper subscribers. That's great news for Android users who have put up with inferior Instapaper substitutes, since Mr. Arment doesn't have the time or desire to build an Android version of the app.

ajeffries [at] observer.com | @adrjeffries