P2P Poll App

A peer-to-peer polling app built with Automerge and Vanilla JS. No backend required — polls sync in real time across browsers using CRDTs and a WebSocket relay.

Features

Add options — type an option and press Enter or click "Add Option". Duplicate options (case-insensitive) are rejected with an inline error message.
Vote on options — click the vote button next to any option. You can vote on multiple options, but only once per option.
Toggle votes — click your vote again to remove it (the button turns green with a checkmark when you've voted).
Live vote counts — options are sorted by vote count in descending order and update in real time as votes come in from other users.
2-minute countdown timer — click "Start 2-min Vote" to begin a shared countdown. Voting is open before and during the countdown. Once the timer expires, all vote buttons are disabled.
Shared timer — the deadline is stored in the Automerge document, so all peers see the same countdown and voting closes simultaneously for everyone.
Copy URL — click "Copy URL" to copy the poll link to your clipboard. Share it with others to join the same poll.
P2P sync — all state (options, votes, timer) syncs across browsers in real time with no central server handling your data.

How it works

Tech stack

Automerge via @automerge/vanillajs — a CRDT library that lets multiple clients concurrently edit shared documents and merge changes without conflicts.
BroadcastChannelNetworkAdapter — syncs between tabs in the same browser instantly via the browser's BroadcastChannel API.
WebSocketClientAdapter — syncs across different browsers/devices via a WebSocket relay (wss://sync.automerge.org). The relay only forwards CRDT messages; it does not store or interpret your data.
IndexedDBStorageAdapter — persists the document locally so it survives page refreshes.
Vite — bundles the app with WebAssembly support (required by Automerge).

Data model

The poll is a single Automerge document with three fields:

{
  options: string[],       // list of poll options in insertion order
  votes: { [option]: number }, // vote count per option
  deadline: number | null  // Unix timestamp (ms) when voting closes, or null
}

Each document gets a unique Automerge URL (e.g. automerge:abc123...) stored in the page's URL hash. Opening the same URL in any browser loads and syncs the same document. Creating a new poll generates a new document and updates the hash automatically.

Voting rules

Voted options are tracked in localStorage (keyed by document URL), so they persist across page refreshes but are isolated per browser.
One vote per option per user. Votes can be toggled off and back on until the timer expires.
The timer (doc.deadline) is set once by whoever clicks "Start 2-min Vote" and is shared via the Automerge document, so all peers use the same deadline.

Running locally

pnpm install
pnpm dev

Open the printed localhost URL. To test cross-browser sync, copy the URL (including the #automerge:... hash) and open it in a different browser.

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