To provide a better identity for photos, Facebook has now adapted Advanced face recognition technology. From this, Facebook can detect your face even you are not tagged.
Facebook can detect your face even you are not tagged:
Yesterday (December 19, 2017) Facebook announced a new optional tool to identify your face on any uploaded image across the facebook. This will help you in a lot of ways. If anyone uploads a photo, Facebook will automatically detect your face if it there in the photo. It will send you notification of the confirmation. If someone uses your photo for other profiles (most likely fake profiles), it will immediately notify you asking whether it is you or not.
How does it work?
Facebook will analyze the pixels in photos which you are already tagged. Then it generates a string of numbers called as a template. When anyone uploads a photos or videos are, Facebook will compare those images to the template. You can enable or disable in face recognition settings.
If you are in a photo, Facebook will send you a notification, even if you haven’t been tagged. You’re in control of your image on Facebook and can make choices such as whether to tag yourself or leave yourself untagged. You can even reach out to the person who posted the photo if you have concerns about it.
Article and image source: Facebook Newsroom