"altmetrics is the creation and study of new metrics based on the Social Web for analyzing, and informing scholarship." (http://altmetrics.org/about/)
Alternative metrics, or altmetrics, involve evidence of discussion happening online, including links, shares, views, and downloads in social media, blogs, and other venues, which can demonstrate popular or societal impact in areas such as education, public policy, etc.
"Correlation and factor analysis suggest citation and altmetrics indicators track related but distinct impacts, with neither able to describe the complete picture of scholarly use alone." - Jason Priem, Heather Piwowar, and Bradley H. Hemminger, "Altmetrics in the Wild: Using Social Media to Explore Scholarly Impact"
As the brief intro video below concisely states, altmetrics are "meant to complement, not replace, citations."
NGL's Engine Orange search engine: includes "Plumprint" to illustrate altmetrics data from PlumX Metrics
Other databases including Elsevier's ScienceDirect, Wiley Online Library, and Taylor & Francis Online: incorporate article-level metrics for some or all content (often sourced through the company Altmetric, so largely consistent across platforms)
In a selected article: look for a colorful Metrics bar or wheel to see altmetrics from different sources or channels
Related blog post from Elsevier: "Article level metrics: a valuable way to gauge an article’s real-time impact" (3 Sept 2015).
One click displays altmetric data for an article you're reading on the web (your own work or someone else's). Be aware that stats from Altmetric.com may only be accurate back to a 2011 publication date.
(Note: Article must include a Digital Object Identifier, or DOI, for the bookmarklet to work.)
If you know an article's DOI (Digital Object Identifier), you can use it to look up PlumX Metrics for that article for free. Just add the DOI to the end of this URL: https://plu.mx/a/?doi=