Background <p>Osteoporosis is a complex disease with multiple causes and treatments, making access to accurate online health information (OHI) critical for informed decision-making amid rising digitization and misinformation. This study aimed to evaluate whether current OHI on osteoporosis meets the criteria for evidence-based health information (EBHI) to support informed decisions.</p> Methods <p>We conducted a descriptive cross-sectional study to evaluate the quality of OHI in German and English. The search terms “osteoporosis” and its German translation were used in Google searches, which were independently screened by two reviewers. An initial exploratory search covering the first five result pages in each language was conducted in March 2021, followed by an extended search in September 2021 that included the first ten pages of results. Websites were included if they targeted laypeople, offered at least two options (including waiting or doing nothing), and were presented in a coherent way. Quality was assessed using the validated “Mapping the Quality of Health Information” (MAPPinfo) checklist. To develop a shared understanding of how the criteria should be applied to the specific health problem of osteoporosis, a subset was independently assessed by two raters, with the remaining assessments conducted individually. Data analysis included the calculation of mean scores (0–100%), which represent the compliance with the EBHI criteria.</p> Results <p>146 websites met the inclusion criteria (81 German, 65 English) and came from various sources, including pharmaceutical companies (30%), hospitals (35%), government agencies (16%), specialist organisations (10%), non-profit organisations (8%), patient organisations (4%), health insurances (3%), and other providers (4%). Websites covered OHI on diagnostics (<i>n</i> = 120), treatment (<i>n</i> = 136), prevention (<i>n</i> = 102), and rehabilitation (<i>n</i> = 1), with 92% addressing multiple areas. On average, the information quality of the OHI is 15.3% (SD = 5.2), 16.7% (SD = 5.7), and 17.4% (SD = 5.6) for diagnostics, treatment, and prevention, respectively.</p> Conclusions <p>Current OHI on osteoporosis often fails to meet basic standards of EBHI, highlighting the urgent need to improve the quality to support informed decision-making. As the use of OHI increases, ensuring that these resources are reliable and evidence-based is critical to improving patient outcomes.</p> Clinical trial number <p>Not applicable.</p>