# Versus

> Rank anything by pairwise comparison: pick the better of two, duel after duel, and the ranking builds itself. Text, images or colors. Free, no account.

Versus is a free web app that ranks a list of anything (places, photos, products, colors, names) by showing two items at a time and asking which one wins. Each answer is a duel; a scoring method turns the duels into a ranking with a measure of how settled it is. It runs in the browser: rankings are stored on the device, with no account.

## Features

- Duels with buttons, arrow keys or swipe, with undo, skip and ties
- Items of any kind: text, images, solid colors and gradients
- Four scoring methods, switchable at any time without losing a duel
- Results with a podium, a ± margin per item and a comparison of the methods
- English and French, light and dark themes
- Local-first: rankings stay in the browser, no account needed
- Installable as an app that works offline

## Scoring methods

Every method is recomputed from the same duel history, so switching loses nothing.

- **Balanced (default)**: Bradley-Terry model fitted on all duels at once, with a ± standard error per item. Order-independent: best for things that do not change, like photos or products.
- **Dynamic**: Elo rating updated duel by duel (K = 40 for an item’s first 6 duels, then 24). Order-dependent by design: for preferences that evolve.
- **Simple**: Smoothed win rate, (wins + ties / 2 + 1) / (duels + 2). The easiest to read.
- **Exact sort**: Binary insertion sort replayed from the duels: no ties, no skips, and a full order in the fewest duels.

## Links

- [Versus](https://versus.steevepommier.com/): home page, in English
- [Versus en français](https://versus.steevepommier.com/fr/): home page, in French
- [The app](https://versus.steevepommier.com/app/): start ranking (English or French)
- [Source code](https://github.com/CostardRouge/versus): TypeScript, MIT license
- [Legal notice and privacy](https://versus.steevepommier.com/legal/): publisher, hosting, what is stored and counted
- [Steeve Pommier](https://steevepommier.com/): author