One interesting pattern I’ve noticed popping up around my favorite new apps these days is that they follow what I’d call a “cloudtop” design. I thought I’d share my own notes on this pattern primarily so that people I’m talking to know what I’m prattling on about, but also in case anybody else finds the concept useful.

Great web apps like Dropbox (affiliate link) and Evernote aren’t merely web services that happen to have APIs, or simple desktop apps; They live in a sort of new in-between state that seems to be delivering the promise of past hype like Microsoft’s “Software Plus Services” slogan.

The key traits of a cloudtop app are:

• The app is designed with the assumption that you work and live across multiple devices, with broadly varying capabilities.
• While the app performs synchronization tasks, there’s no “synching” action, its handles that function (often alongside version control and conflict resolution) automatically.
• Cloudtop apps are delivered as native code on nearly every supported platform, from desktop computers to smart phones, with an interface that scales appropriately.
• While the app may have a web interface, that’s largely a convenience and is not usually the primary way in which you interact with the app.
• These apps often adopt a freemium model, with payment introduced in a very obvious way based on usage.
• Though they have native first-party clients, APIs allow for the app to become a platform for other developers, as with the Elements text editor or AirDropper uploads for Dropbox, or any of the apps listed in the Evernote Trunk directory.

In this pattern, iTunes isn’t really a cloudtop app, despite having native clients on iPhone and on Windows and Mac, because it doesn’t easily, let alone automatically do synchronization of libraries between those platforms. Netflix, despite starting as a disc delivery service, is rapidly evolving into what feels like a cloudtop platform — my library is available anywhere with great native apps on many devices, and it syncs my history and queue automatically.

Twitter may evolve into a cloudtop platform if its native clients win on every platform, but the fact that its primary use is far and away through its HTML web interface, it doesn’t seem as if that’s likely, and other aspects like a freemium business model or really robust synching (all my clients show a different subset of my DMs) don’t seem to be a priority. Cloudtop apps seem to use completely proprietary APIs, and nobody seems overly troubled by the fact they have purpose-built interfaces.

One last, interesting note about this class of apps: They have social functions like sharing, but they’re not really fundamentally social apps. I can share a Dropbox folder or Evernote notebook with you, but that’s not the primary means of discovery. Word of mouth is what drives adoption, and there’s little to no integration with networks like Facebook or Twitter, with the apps relying instead on good old-fashioned email for a lot of their social function. I’m not quite sure what that means, but there’s some lesson there, especially given that these apps are very popular with a lot of mainstream, non-techie users.