MD5 Hash for Gravatar — Generate Avatar URL Hash
Quick Answer: Gravatar uses the MD5 hash of your lowercase, trimmed email address to generate avatar URLs. Enter your email to get the hash, then use it at: https://www.gravatar.com/avatar/[hash].
FAQ
How does Gravatar use MD5?
Gravatar URLs follow the format gravatar.com/avatar/[md5(email)]. The email must be trimmed of whitespace and lowercased before hashing.
Is MD5 secure enough for Gravatar?
For Gravatar, MD5 is fine -- it is used as an identifier, not for security. Reversing an MD5 hash to get an email is impractical for this use case.