Advanced online election counting

Count instant runoff and single transferable vote elections for free, no downloads or sign-up required

Screenshot of OpenTally

Key features

Runs in your browser

No downloads or sign-ups are required. OpenTally counts are computed entirely inside your browser, and no data ever leaves your computer.

Wide range of STV systems

OpenTally supports Gregory (inclusive and exclusive, weighted and unweighted), Meek and Wright variants of the single transferable vote.

Support for arbitrary constraints

OpenTally is the only publicly available election counting software to support arbitrary combinations of constraints, such as gender quotas and other affirmative action requirements.

Free and open source

Source code for OpenTally is publicly available under the GNU AGPLv3.

From our blog

Latest news and posts from the OpenTally blog

Dev Log
Implementing a BLT parser by hand in Rust (vs pest and combine)

OpenTally is open-source software which can count single transferable vote elections specified using the BLT file format.

Earlier this month, I replaced OpenTally's previous naive string-manipulation-based BLT parser with one using pest. A new parser was necessary to support extensions to the BLT

Dev Log
Asyncify with vanilla JS/WebAssembly (wasm-bindgen compatible)

WebAssembly is a technology for executing compiled programs in the web browser at near-native speeds. However, it has a number of current limitations, including that it does not support coroutines/asynchronicity.

In OpenTally, WebAssembly is used to run code for counting an election. This…

Model rules for a single transferable vote election using the weighted inclusive Gregory method

OpenTally is open-source software for counting single transferable vote (STV) elections. The default preset in OpenTally is ‘OpenTally WIGM’, a recommended set of simple STV rules designed for computer counting, using the weighted inclusive Gregory method, exact quotas and rational arithmetic. …