WordPress at a glance
filter is not described

pre_get_avatar filter-hook . WP 4.2.0

Filters whether to retrieve the avatar URL early.

Passing a non-null value will effectively short-circuit get_avatar(), passing the value through the 'get_avatar' filter and returning early.

Usage

add_filter( 'pre_get_avatar', 'filter_function_name_9854', 10, 3 );
function filter_function_name_9854( $avatar, $id_or_email, $args ){
	// filter...

	return $avatar;
}
$avatar(string)
HTML for the user's avatar.
Default: null
$id_or_email(mixed)
The Gravatar to retrieve. Accepts a user_id, gravatar md5 hash, user email, WP_User object, WP_Post object, or WP_Comment object.
$args(array)
Arguments passed to get_avatar_url(), after processing.

Where the hook is called

get_avatar()
wp-includes/pluggable.php 2504
$avatar = apply_filters( 'pre_get_avatar', null, $id_or_email, $args );

Where the hook is used (in WP core)

Does not used.