Some tools ask you to download a "viewer software" or browser extension. These can:
Instagram is owned by Meta (Facebook), a company that invests billions in cybersecurity. When a user sets their account to private, the server stops serving media content (photos/videos) to anyone who is not on the approved followers list. Some tools ask you to download a "viewer
If you share friends with the person, you might see their tagged photos on your mutual friends' public profiles. Some tools ask you to download a "viewer