Risk-Limiting Audits with Arlo


Democracy depends upon trust in the electoral process. In the United States, nearly every jurisdiction relies on machines to tally votes, so trusting the process means trusting the machines that scan and tally our paper ballots. Given the high stakes of our elections, and our adversaries’ demonstrated interest in them, what can we do to double-check the equipment producing the tallies?

The Risk-Limiting Audit

The best safeguard we have against hacked or otherwise faulty voting systems is a Risk-Limiting Audit (RLA). Experts believe that RLAs are the most efficient way to gain certainty that the winner reported by the voting system is correct.

The RLA is efficient because of its insight that we do not need to manually recount every vote to gain certainty in the outcome of an election. Instead, the number of votes we need to manually count depends on the margin of victory in the contest we’re auditing. A typical state-wide RLA might require checking fewer than 1000 ballots to validate an entire state’s election results.


In 2017, Colorado became the first state to implement rigorous RLAs, auditing one race in each of 50 of its 64 counties. Colorado’s experience helped to create the requirements for software that is used to run RLAs today. VotingWorks is proud to lead the development of this software “Arlo”, building on the pioneering work done by Colorado and its technical partner, DemocracyWorks.

Open Source

The code for Arlo is open source and freely available for anyone to use and host.

VotingWorks Hosting & Support

VotingWorks provides a hosted Software-as-a-Service version of Arlo to states and local jurisdictions that want it. VotingWorks’ hosted service runs in the cloud. Our cloud provider, AWS, conforms to security standards including SOC 1/SSAE 16/ISAE 3402, SOC 2, PCI DSS Level 1, ISO 27001, and FISMA. See https://aws.amazon.com/compliance/ for more details.

Voting Works provides its hosted version of Arlo for the annual fee listed below, which includes support. There is a one time $5,000 set-up fee to get started. Arlo is free to all states and local jurisdictions in 2019 and the set-up fee shall be waived for all states and local jurisdictions that begin using Arlo in 2019.

Interested in learning more? Send us an email at rla-info@voting.works.

Registered Voters in State Annual Fee Registered Voters in Local Jurisdiction Annual Fee
Less than 2,000,000 $17,500 Less than 250,000 $5,000
2,000,000 - 7,000,000 $30,000 250,000 - 500,000 $10,000
7,000,000 - 10,000,000 $45,000 500,000 - 1,000,000 $15,000
10,000,000+ Contact us More than 1,000,000 Contact us


If you are running your first RLA, you should not view Arlo as a substitute for the knowledge and skill that an experienced RLA consultant can provide to help you get started. Risklimitingaudits.org can point you to consultants who can help you run your first RLA and build the capacity to run future RLAs independently.