The avatar on an Instagram profile is displayed at thumbnail size — but the actual image is much larger. This viewer retrieves the bigger version, so you can finally see the avatar clearly.

When you open a profile, Instagram renders the avatar as a small rounded square. Underneath that crop, a higher-resolution image file exists for every public account. The avatar viewer fetches that underlying file, so what you inspect is the avatar itself — not a pixelated thumbnail.
The circle you see in the app is a display crop. The source image behind it is what this viewer retrieves.
No upscaling tricks are used — the larger preview is the same file displayed at its native size.
Zooming into a screenshot only enlarges the pixels. Opening the source file keeps every pixel sharp.
The lookup is limited to publicly visible avatars. Private accounts are never accessed.
A quick look at the numbers behind Instagram avatars.
typical display size of an avatar thumbnail in the app
the source file the viewer can open for public avatars
is all the viewer needs to find the avatar
The viewer matters whenever the thumbnail is not enough.

Straight answers about avatars, sizes, and how the lookup works.
Enter a public username and see the avatar the way it actually exists — sharp and full-size.