The size parameter that does nothing
GitHub avatar links accept a query parameter, ?s=460, that is widely described as controlling resolution. Testing it produced an identical byte count at every value:
| Requested | File size |
|---|---|
| Default (no parameter) | 28,573 bytes |
| s=460 | 28,573 bytes |
| s=1024 | 28,573 bytes |
| s=2048 | 28,573 bytes |
The reason is that s caps the size rather than setting it. When the stored image is already smaller than the number requested, GitHub serves the original unchanged. Asking for 2048 pixels does not manufacture them. So this tool omits the parameter and serves the stored file directly, which is the largest version that exists.
Gravatar accounts
Some older accounts never uploaded an avatar to GitHub and instead show one from Gravatar, keyed to the email address. Those still resolve normally here, because GitHub returns the effective avatar URL either way. What differs is that the image lives on Gravatar's servers rather than GitHub's.
Accounts with no avatar
An account that has never set a picture gets an identicon — the small geometric pattern generated from the user ID. These are produced on the fly, so what you download is that generated pattern rather than a photograph.
Organisations work too
Organisation avatars use the same endpoint as user accounts, so a name like facebook or microsoft returns the organisation's logo. No separate lookup is needed.