What kanban is, and why the work-in-progress limit is the whole idea

Kanban is a Japanese word meaning signboard, a Toyota production idea from the 1950s, and — since the 2000s — the most copied layout in software: three columns, cards moving left to right. Most people who use a kanban board have never been told what it's for, so they use it as a fancy to-do list and miss the one mechanism that makes it work. This guide fixes that, for teams and for the personal board on this site.

From Toyota's factory to your to-do list

On Toyota's assembly lines, a kanban was a physical card that travelled with parts: when a station used up a bin, the card went back upstream as the signal to make more. Nothing was produced until something downstream pulled it — the opposite of pushing work through and letting it pile up. The insight was that the pile-up itself (inventory, half-finished work) was the waste. In 2004 David Anderson applied the same pull principle to software teams at Microsoft, and the visual board with columns for each stage became the standard.

The board: columns, cards, flow

Columns are the stages work passes through — at minimum To do, Doing, Done; a real team might have Backlog, Ready, In progress, Review, Done. Cards are units of work, one each. The rule is that cards only move right, and the board is read as a picture of flow: where cards cluster, that stage is a bottleneck. A card that has sat in Review for a week is visible to everyone in a way a line in a spreadsheet never is. That visibility — not the columns — is the first benefit.

The WIP limit is the point

The second benefit is the one that gets dropped: a limit on work in progress. Each column gets a maximum (say, three cards in Doing), and when it's full nobody starts anything new; they finish or help something along. This feels wrong and works, for a reason from queueing theory called Little's law: the time an item spends in a system equals items in progress divided by the completion rate. Halve the work in progress and everything finishes twice as fast, at the same effort, because there is less switching and less waiting. A board without WIP limits is a to-do list with extra steps. With them, it's a machine for finishing things.

Personal kanban that actually works

For one person the same rules apply, simplified. Keep Doing to two or three cards; if you want to start a fourth, something must move to Done or back to To do. Break cards down until each is a day or less — "Write report" sits for weeks, "Draft section 2" moves. Clear Done weekly, and look at what's stuck. Add columns only for real stages you pass through (Applied / Interviewing / Offer for a job search; Waiting for a card blocked on someone else). A personal board needs no accounts or sync, which is why one that lives in your browser is enough; To-do list methods that actually work compares the alternatives, and the Pomodoro timer pairs with the Doing column.

Kanban versus to-do lists and scrum

A to-do list is a backlog with no notion of in-progress, which is why long lists breed half-finished work. Scrum plans work into fixed sprints with ceremonies; kanban has no sprints — work flows continuously and the board is the plan. Teams often blend them ("scrumban"). For a solo worker or a small team with a steady stream of varied tasks, kanban's low ceremony wins; for a project with a hard deadline, a timeline answers the question the board can't: when.