C-CDA is the HL7 XML format every U.S. EHR exports for transition-of-care documents — discharge summary, continuity of care document (CCD), referral note, history & physical. Required for ONC certification and Meaningful Use / Promoting Interoperability incentive programs. Templates standardize how to represent allergies, medications, problems, vital signs, lab results across vendors. Files are typically 100KB-2MB of XML; the document is human-readable when rendered with a stylesheet.
How to open
Most browsers render C-CDA inline if the embedded XSL stylesheet loads. EHR portals (Epic MyChart, Cerner HealtheLife) auto-render. Standalone viewers: HealthIT.gov C-CDA Renderer, Lantana CDA Validator. Convert to HTML for portable viewing.