Dossia is a Personal health record service offered by some of the largest employers in the United States. Along with Microsoft's HealthVault, Dossia is one of the largest PHR deployments in the worldUnlike Microsoft's PHR effort, Dossia is based on open source software. Dossia released their API in summer of 2009.Dossia differs from traditional tethered PHR services by providing user access to health information regardless of health plan, employer, or physician.