Dropbox

Dropbox was founded in 2007 by MIT student Drew Houston, together with co-founder Arash Ferdowsi, to solve a simple problem: keeping files in sync across devices.

After joining Y Combinator, they spent the summer writing code to build a syncing product far better than any existing service. Rather than finish the whole thing first, Houston looked for the cheapest way to find out if anyone wanted it.

Building a reliable sync engine for every operating system takes months. Houston needed to know demand existed before he spent that time. So instead of shipping code, he recorded a four-minute screencast showing Dropbox's core sync feature in action

• Recorded a short demo video instead of finishing the product

• Showed a file syncing automatically across folders and devices

• Shared the video directly on tech forums like Hacker News and Digg

• Used sign-ups, not shipped code, to measure real demand

The screencast wasn't a finished app, but it clearly conveyed the idea. When it spread across tech forums, the beta waiting list jumped from 5,000 to 75,000 overnight, giving Dropbox strong validation before most of the code was ever written.

Houston's core hypothesis was that flawless file-syncing would be a killer feature, one that solved a problem users didn't even realize they had.

To test the idea with minimal effort, Houston took a lean, sequential approach.

Once the video validated the idea, Dropbox built the full product across Windows, Mac, and Linux, using early adopters for feedback at every step.

• An MVP doesn't need to be working software, it needs to prove demand

• Sign-ups and shares are real evidence, opinions are not

• Build the full product only after demand is proven