Arlo is software for managing and conducting a Risk-Limiting Audit (RLA). The code for Arlo is open-source and freely available for anyone to use and host. VotingWorks provides a hosted version of Arlo and customer support when conducting an RLA.
Arlo supports ballot polling, batch comparison, ballot comparison, and hybrid RLAs for single jurisdiction to statewide audits.
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RiskLimitingAudits.org describes the history and process of conducting an RLA.