Ever notice that you seem to spend 80% of your time on 20% of your tasks? Or that 80% of the decisions in a meeting seem to occur in 20% of the meeting time? Welcome to the world of the 80:20 rule. When we design, build and test software, we have to determine where to start and what we should do next. The 80:20 rule helps provide an answer to these questions, while helping to increase our productivity and effectiveness. As well as being an agile principle, it’s a common thread in other disciplines, and there’s a special variation that applies to software defects. We’ll explore the different ways testers and developers are using the 80:20 rule. This rule could be a secret ingredient to help you build software smarter!