When you read and comment on blogs, you see there are some default icons (commonly on a gray background a white guy) and some profile pictures are shown next to the commenter’s name. This is called Avatar. Commenter doesn’t need to upload any profile picture on each blog. Blog owners do not allow uploading picture for the unregistered users. Question is how this is possible to show profile photo with comments as a guest user or simple visitor?
Yes, it is possible because of Gravatar. Gravatar.com is an awesome neat website that allows you to host an avatar and use it all over the web.
Gravatar is linked to the email address. Retrieve the avatar for a user who provided a user ID or email address. Most commonly used in the comments section.
Your Gravatar is an image that follows you from site to site appearing beside your name when you do things like comment or post on a blog. Avatars help identify your posts on blogs and web forums.
On Gravatar, users can register an account based on their email address, and upload an avatar to be associated with the account. Gravatar plugins are available for popular blogging software; when the user posts a comment on such a blog that requires an e-mail address, the blogging software checks whether that e-mail address has an associated avatar at Gravatar. If so, the Gravatar is shown along with the comment.
Most blogging applications have support for Gravatar like WordPress, Blogger etc.
A Gravatar avatar can be up to 512 pixels wide, is always square and is displayed at 80 by 80 pixels by default. If the uploaded avatar is larger or smaller, the avatar is scaled appropriately.
If you want to be identified on the web, then you should use a gravatar. If you are a blogger, non-profit, small business, or anyone who wants to build a brand, then you need to start using gravatar.