An N-back test shows a stream of letters and asks whether the current letter matches the one shown n steps earlier. In this free online version you start at 3-back and the letters speed up from 2000 ms to 1200 ms as you level up, so it trains working-memory updating, not just storage.
Unlike passive span tests that measure raw storage capacity, the N-Back task requires participants to continuously update a dynamic mental buffer. As letters appear in rapid succession, users must decide whether the current letter matches the one presented exactly N steps earlier (starting at 3-back, progressing to 4-back and beyond), constantly ejecting old tokens and encoding new stimuli.
How this is measured: every event is timestamped with the browser's performance.now() high-resolution clock, entirely on your device -- no score is uploaded. Browser timers are deliberately coarsened as a Spectre mitigation (typically to about 1 ms), and your display quantizes each change to its refresh interval, about 16.7 ms per frame at 60 Hz (Woods et al., 2015). Treat differences smaller than about 5 ms as measurement noise, and compare your own runs on the same hardware.
Data transparency: SkillDrills collects no aggregate data. Your scores and settings live only in your browser's localStorage and are never uploaded, so this site publishes no user averages, percentiles or player counts. Every figure quoted here comes from the published work in the References panel below.
This drill is a free browser game for practice and interest. It is not a medical device, a diagnostic instrument, or a screening or treatment tool for any condition, and no score here says anything about your health. If you have concerns about your memory or thinking, speak to a qualified clinician.