Behind the scenes of the little green syncing icon at Google I/O

APR 04, 2008
By Steven Saviano, Software Engineer

This post is one in a series that previews Google I/O, our biggest developer event in San Francisco, May 28-29. Over the next two months, we'll be highlighting sessions and speakers to give Google Code blog readers a better sense of what's in store for you at the event. - Ed.

Being a UI engineer, I usually expect the features I implement to have a little bit more visual interaction than a little green icon. However, while my team and I were implementing Google Docs Offline, the challenge was just that: how make the offline experience work seamlessly while just adding one icon.

Building Docs Offline was quite a challenge, and we pushed Gears to its limits to accomplish it. To give an idea of some of the complexities, Google Docs is one application that is comprised of 3 editors (documents, spreadsheets, and presentations) and 1 file management UI running across two domains ( and The domain challenges alone were significant challenges in our design - we are fully utilizing multiple cross-domain workers to synchronize documents, capture resources, and authenticate users.

Oh yeah, and did I mention that any of the servers can be running any version of the code and fall over at anytime?

Getting all of this to "just work" for users was tough, but necessary for a great user experience.

Wondering how you can take your applications offline? I'll be discussing all these issues in-depth at this year's Google developer conference, Google I/O. Come by and learn how to get your app its very own little green syncing icon.