Google Images: Visit images.google.com and click on the camera icon on the right side of the search field. This will allow you to search by image. You can either upload the image you want to search with or paste the URL of the image.
PimEyes Face Recognition Search Engine: This search engine uses face recognition technology to perform a reverse image search. You can upload the image you want to search with and it will show you where the image appears online.
TinEye: This is another reverse image search engine that allows you to search for a person by photo. You can upload the image or paste the URL of the image, and it will present you with all the results where the photo is posted.
I hope this helps! Let me know if you have any other questions.