What is Elevators?
Elevators is a free interactive article that explains why the elevator never seems to come when you press the button. It walks through the algorithms elevators use, starting with SCAN, patented in 1961, and LOOK, the one most people expect, and then on to how a group of cars decides who picks up whom.
Every idea comes with a live simulation of a building. You can add calls, run the elevators at 1x, 5x or 25x speed and watch how wait times change, then see why engineers measure the whole distribution of waits rather than the average. It was one of the most upvoted Show HN posts of 2026.
Main Features
- Live elevator simulations inside the article
- Speed controls from 1x to 25x
- Single-car and multi-car algorithms explained
- Charts of real wait-time distributions
- Plain language, no maths background needed
How to Get Started with Elevators
- Open john.fun/elevators.
- Read from the top and play with each simulation.
- Add calls and change the speed to see the algorithm react.
- Compare the wait-time charts as the algorithms improve.
Elevators Pricing
Elevators is free in your browser, with no account needed.
Who Should Use It?
- Curious people who wonder why elevators are slow
- Students learning about algorithms
- Fans of interactive explainers like The Pudding
Elevators Alternatives
- The Puddingvisual essays that explain culture with data
- The Evolution of Trustan interactive guide to game theory
- Parable of the Polygonsa playable essay about bias
Frequently Asked Questions
Is Elevators free?
Yes. It is a free interactive article in your browser.
What does Elevators explain?
How elevators decide which floors to visit, from the SCAN and LOOK algorithms to how several cars share the calls, and how wait times are measured.
Who made Elevators?
It is published on john.fun, a site of interactive projects.