Definition
Tesler’s Law (conservation of complexity): every application has an inherent amount of irreducible complexity that cannot be removed — only moved. Making the user-facing surface simple usually means the system (or the designer) absorbs the complexity.
Origin
Attributed to Larry Tesler (Xerox PARC, ca. 1984) in HCI / interaction-design discourse. Popularised for product teams via interviews (e.g. Saffer) and teaching frames such as Yablonski’s Laws of UX. Often taught beside the “illusion of simplicity” — what feels effortless in use is engineered behind the curtain.
Mechanism
If the target experience is simple (feel calm, one-tap journal, phone to tile → bath starts), someone must own the branching logic, timing, defaults, and failure paths. Pushing complexity onto the user shows up as micro-choices, forgotten rituals, and evening collapse. Moving complexity into the system (forms, NFC, notifications, AI project instructions) raises surface simplicity while increasing backend design load.
Applications
- Design personal OS so the desired feeling stays simple while capture, review, and cues stay complex in the background.
- Prefer friction removal (earlier harvest, stacked habit) over asking a fatigued self to “just be disciplined.”
- When building with AI, put complexity into project instructions and knowledge files so daily input stays short.
Sources
Cite
- Yablonski, J. (2020). Tesler’s Law (in Laws of UX). O’Reilly Media.
- Saffer, D. (2009). Designing for Interaction — Tesler interview. New Riders.
Related doctrine
System Within the System
Efficiency vs Effectivity
Journaling is a game-changer
All Success Lies in Its Preparation
extreme discipline → extreme freedom