# Versus

Rank anything by comparing two items at a time — text, images or colours — then publish the ranking and let a crowd vote on it live.

Source: https://steevepommier.com/projects/versus/
Section: Projects
Published: 2026-09-29
Updated: 2026-10-09
Tags: ranking, pairwise comparison, local-first, real-time, PWA, i18n, TypeScript, Vite, Cloudflare Workers, Durable Objects, Cloudflare D1, Cloudflare R2, Vitest, Playwright

---

Picking a favourite out of twenty is hard; picking one of two is easy. Versus
asks only the easy question — this one or that one — again and again, and turns
those quick duels into a real ranking, with a podium and a margin of error.
Items can be text, images (dropped or pasted, downscaled in the browser) or
colours and gradients from an inline editor; a whole list pasted at once
becomes items too.

## Four ways to score the same duels

Every duel is kept, so the scoring method can change at any time without
losing a vote:

{% table %}
- Method
- Algorithm
- Best for
---
- Balanced (default)
- Bradley-Terry, fitted on all duels at once, with a ± margin per item
- Things that do not change: photos, products
---
- Dynamic
- Elo, duel by duel
- Preferences that drift over time
---
- Simple
- Smoothed win rate
- Readability
---
- Exact sort
- Binary insertion sort
- Settling a short list in the fewest duels
{% /table %}

The results page can put two methods side by side, which shows where a ranking
is still fragile. Pair selection favours items with few duels, close
positions and unseen pairs.

## Local first, published on request

The app runs in the browser, keeps everything in `localStorage`, installs as a
PWA and works offline. Only what you publish leaves the device: a published
board gets a link, and a crowd votes on it in real time — one Durable Object
per board holds the votes and the WebSockets, a D1 registry lists the boards,
pictures wait in R2 until they are approved. Rankings, a crowd's result or a
single duel can be shared as an image drawn in the browser, and a board's link
unfurls with its own card.

It ships in English and French, the home page included, with no UI framework
and three runtime dependencies — all of them fonts.