Altmetrics have a number of advantages over citation-based metrics:
Complement citation-based metrics: Altmetrics provide a wider range of data, from a wider range of sources than citation-based metrics. Altmetrics can measure impact and visibility outside the academic world, where people may use but not cite scholarly work. Altmetrics data is also highly nuanced and can be provided in high detail and in the context in which it originates.
Capture a record of attention:
This class of metrics can indicate how many people have been exposed to or are engaged with a scholar's work. This metric includes the number of mentions on Twitter, article pageviews, downloads, or GitHub repository watchers.
Show a measure of dissemination:
These metrics (and the underlying mentions) can help you understand where and why a piece of scholarly work is being discussed and shared, both among other scholars and in the public sphere. Examples of this include coverage in the news, social media sharing, and blogs.
Indicate influence and impact:
Some of the data gathered via altmetricscan signal that scholarly work is changing a field of study, the public’s health, or having any other number of tangible effects upon larger society. Examples of this include references in public policy documents or commentary from experts and practitioners.
Accumulate faster than citation-based metrics:
By virtue of being sourced from the Web and not from journals and books, it’s possible to monitor and collate mentions of work online as soon as it’s published.
Can capture more diverse impacts than citation-based metrics:
Altmetrics can complement citations in that they help show the many ‘flavours’ of impact scholarly work can have. For example, altmetrics data can help scholars understand how their work is being interacted with by the public, government, policy makers, and other scholars.
They apply to more than journal articles and books:
Scholars are sharing their data, software, presentations, and other scholarly outputs online more than ever before. Altmetrics are useful in tracking this use on the Web as easily as can be done for articles and books.
Open access advantage Altmetrics providers pull their data from open sources, who give access to their APIs or raw usage data, which makes data more easily replicable than data in proprietary databases.