What is Poka-yoke?
Poka-yoke (Japanese for ‘mistake-proofing’) is a design approach from Toyota’s production system that prevents errors by making incorrect actions physically impossible or immediately obvious. Applied to behavioral design, it means building systems where the wrong action cannot be completed.
How it works
Shigeo Shingo developed poka-yoke in the 1960s at Toyota. The approach uses two strategies: prevention (the error cannot physically occur, like a SIM card that only fits one way) and detection (the error triggers an immediate signal, like a car dashboard warning when seatbelts are unbuckled). In digital design, poka-yoke includes disabling submit buttons until required fields are complete, preventing users from entering letters in phone number fields, and requiring confirmation before irreversible actions.
Applied example
A gas pump nozzle designed so that diesel fuel hoses physically cannot fit into unleaded fuel tanks is a mechanical poka-yoke that eliminates misfueling errors entirely rather than relying on the driver to read labels and remember which fuel their car uses.
Why it matters
Poka-yoke is superior to training and warnings because it works at the system level: it removes the possibility of error rather than asking humans to be vigilant, which they inevitably fail at under real-world conditions.
