A vanity metric is a kind of metric that may look good (“Wow, you have so many signups!”), but doesn’t help you to move forward with growth, product development, etc. The classic examples of vanity metrics are a number of signups, downloads, etc. If there’s no next action that could be taken based on a metric –it’s probably a vanity one.
Forewarned, forearmed. Let’s calculate how many signups in total do we have and remember – it is just a number, a vanity metric.