Open access to publications through electronic journals has dramatically expanded downloading and use of this literature and spurred the rise of alternative metrics to assess article impact. Open access publications have been shown to gain more citations than articles with restricted access, and seven of the 10 most popular articles in 2012 were free public access with the most response, as documented through altmetrics, coming from non-scientists. Altmetrics also enables post-publication filtering and peer review in a nearly immediate timeframe for very large open access journals. Online activity measured through altmetrics highlights attention to the article on its own, less dependent on the validation of a journal name. The field of altmetrics is young, still limited to certain open websites, but with potential for considerable expansion, development and application. Open access and altmetrics can be expected to grow in a complementary and mutually supportive manner.