Gravatar is a service which associates user-provided images with email addresses to allow an image to follow a person from site to site. Gravatar is enabled by default in WordPress; for each comment on a post calls are made to Gravatar’s database to retrieve images associated with the comment’s email. If no image is associated with the email a default image is used.
The problem with Gravatars is they’re very inefficient. Every single image is requested from the server, even if the image repeats. The images are also only cacheable for 300 seconds. This is terrible for your site’s load time. They may look pretty but the inefficiency of the system is terrible.
Our review of Zagg’s Invisible Shield has over 60 comments on it. Pingdom Tools was reporting over 11 seconds to load. After we completely disabled Gravatar, the page load time jumped down to 6.2 seconds. This saved 60+ requests to Gravatar (just imagine that overhead). Decreasing a page’s load time by 5 seconds is amazing! What a way to decrease your bounce rate and improve your ranking in Google!