The Thumbnail Problem
Instagram made a deliberate product decision years ago not to let users enlarge profile photos, and has never reversed it. Tapping an avatar does nothing. The result is that the picture you see is a downscaled thumbnail — typically a fraction of the uploaded file's dimensions — rendered into a circle with the corners masked off. Screenshotting that and cropping in gives you a soft, pixelated square, because you are enlarging something already thrown away.
The original never left Instagram's servers, though. It is stored at full size and served to whichever client asks for that version. All this tool does is make that request instead of the thumbnail one, which is why the difference is so obvious the first time you use it.
What This Is Reasonable For
The honest common uses are mundane: confirming who a message request is actually from, matching a handle to a face before a meeting, or looking at how a brand has cropped its logo when you are designing your own. There is also the simple case of wanting to see a friend's new photo properly, which the app makes needlessly difficult.
What it is not for is building a picture of someone who does not want to be found, or lifting an avatar to impersonate them. A downloaded file is still someone's photograph and, in the impersonation case, using it will get an account banned and can create real legal exposure. The tool is neutral; what you do afterwards is not.
Other Things You Can Pull From a Public Profile
Profile pictures are the smallest piece. If you are looking at an account, you can also watch their live Stories anonymously, save the Highlights pinned to their profile, or download individual photos and Reels at original quality. All of it works on the same principle: requesting what a logged-out visitor is already served, and none of it involves your account.