Since our founding, we've supported engineers using "20% time" to work on self-directed activities. As we've grown, our view of this time has expanded beyond the traditional "work on side projects" definitions popularized by Google and 3M. We've changed the label to "Self-Directed Time" to reflect what we mean, which is: any self-directed activity that's intended to improve our business.
This isn't comprehensive, but should give you an idea of the many ways that you can use self-directed time. Business leaders who prioritize engineering work can expect that they'll have "most of an engineer's time, most of the time", not "all of an engineer's time, all of the time".
While this type of work will often form a minority of an engineer's time, it is weighed heavily when considering raises and promotions, receiving roughly equal weight with performance on activities directed by the business. One of the key differentiators between the titles "Software Engineer", "Senior Software Engineer", and "Principal Software Engineer" is the amount of (and impact of) self-directed work. More self-directed work is expected at higher levels.
Perhaps it goes without saying, but to be clear: self-directed work does not require approval from anyone. An engineer should be able to explain the intended impact of their work and measure it after it has been completed. Nobody can expect to bat 1000, but hopefully there's a measurable impact some of the time.
We used "20% time" initially since it's a well known concept, but a static 20% is misleading. Someone who's new to the team may initially spend little to no time on self-directed work, while our most senior engineers spend the majority of their time directing their own work. For this reason, and to highlight that this is more than a "work on side projects" suggestion, we changed the label from "20% time" to "Self-Directed Time".