Altmetrics are another source of article level metrics. They capture interest and discussion about articles, to show readership and reach. As with citation data, there are different providers of altmetric data.
(Examples above: Altmetric.com, PlumX Metrics, PLoS)
They can provide a measure of how scholarly publications are shared, used and discussed online. This can give an indication of the influence and engagement of a publication in online newspapers and news services, blogs, citation in wikipedia articles, sharing via social media networks, use in reference management platforms and inclusion in policy documents.