FaceRect is a powerful and free API for face detection. It finds faces (both frontal and profile) on the image specified by URL or uploaded as a file and is able to find multiple faces on a single photo, producing JSON output with a bounding box for each face found. Additionally FaceRect can find face features for each detected face (eyes, nose and mouth).
For more precise face feature detection please see our FaceMark API: https://www.mashape.com/apicloud/facemark
Online demo is available at http://www.apicloud.me/apis/facerect/demo/
Feel free to test the API as much as you like!
The most recent and complete API documentation is always available at http://www.apicloud.me/apis/facerect/docs/