Every product decision rests on at least one assumption that, if wrong, makes the entire effort pointless. I call this the "killer assumption."

Most PMs don't name it. They build, ship, and then explain why the metric didn't move.

Here's how to find the killer assumption before it finds you.

What Is a Killer Assumption?

A killer assumption is the single belief that has to be true for your product decision to be correct. Not all the assumptions — the one that matters most.