Concurrent Counter

Shared counters that everyone sees change at the same time. Create one, send its link to someone, press a button, and the number moves for both of you.

It runs at https://counter.eusebius.tech/. To run it yourself, see CONTRIBUTING.md.

What it does

• Create New Counter on the homepage makes a counter and takes you to its own page.
• Share on that page opens your device's share sheet, and Copy link copies the address, ready to paste to whoever should share the counter. Where there is no share sheet, Share copies the link too.
• Increase and Decrease change the counter by one.
• Every open copy of the page updates as it happens. There is nothing to refresh.
• The app name in the top left corner leads back to the homepage.
• The homepage shows how many counters have been created, and one counter that every visitor shares, to try it out.

For example, two people counting arrivals at different doors can open the same link and both always see the running total.

How it behaves

• No click is lost. If many people press a button at the same instant, every press is counted: 200 simultaneous increases add exactly 200.
• A counter can go below zero.
• If your connection drops, the page reconnects on its own and catches up with the current values.

Languages and appearance

The app is translated into the 20 most spoken languages in the world: English, Mandarin Chinese, Hindi, Spanish, Arabic, French, Bengali, Portuguese, Indonesian, Urdu, Russian, German, Japanese, Nigerian Pidgin, Egyptian Arabic, Marathi, Vietnamese, Telugu, Swahili and Hausa.

It opens in your browser's language when that is one of them, and in English otherwise. The translate button in the corner changes it, and the choice is remembered on that device. Arabic, Egyptian Arabic and Urdu are laid out right to left. A counter's link is the same in every language, so each person who opens it sees it in their own.

The button next to it switches between light and dark, and follows your system setting by default.

Good to know

• There are no accounts. A counter you create isn't listed anywhere, but anyone who has its link can see and change it, so don't use it for anything that needs to be private or protected.
• The link is the only way back to a counter. Keep it, for example as a bookmark.
• Counters can't be renamed or deleted. Each is labelled with the last six characters of its id.
• The translations were not written by native speakers. Corrections are welcome.

Status

Creating, sharing, increasing and decreasing counters with live updates all work. Renaming, deleting and private counters are not planned yet.

Contributing

See CONTRIBUTING.md for how to run it locally, how the live updates work, and the traps to avoid. Coding agents should start at AGENTS.md.

Licence

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the licence along with this program — see LICENSE, or https://www.gnu.org/licenses/.