One way to find someone on social media using just their picture is through a reverse image search. This involves uploading an image to a search engine like Google Images or Yandex, which will then try to find matching or similar images on the web. The search engine scans its database of indexed images to locate where that same picture appears online, which could lead you to the person's social media profiles. This can be a useful technique if you have a picture of someone but don't know their name or usernames.
Another approach is to use a face recognition tool like PimEyes. These specialized search engines are designed to match faces in uploaded images against a wide database, aiming to identify the individual. While these tools may have some limitations, they can sometimes uncover social media accounts associated with a person's face. It's worth noting that the accuracy and effectiveness of these methods can vary, and privacy concerns around facial recognition technology are an important consideration. Ultimately, finding someone on social media with just a picture requires a bit of detective work, but these techniques provide potential avenues to explore.