One namespace, two kinds of page
GitLab puts users and groups in the same namespace, which is why your username can be taken by a group you've never heard of. It also means one URL shape covers both: gitlab.com/yourname resolves to a profile or a group page depending on what exists there.
That makes these codes useful in two very different settings. On a CV or a badge, it points at your profile and your contribution graph. Inside a company, printed on an onboarding sheet or a wiki handout, it points at the group where the repositories actually live.
If you're on a self-managed GitLab instance rather than gitlab.com, use "Any link" and paste your instance URL — the tool encodes whatever address you give it, including internal hostnames that never touch the public internet.
Everything happens in your browser. The QR encoder is built into this page, so your username is never sent to a server, nothing is logged, and there's no daily limit. The code is static — the link lives in the pattern itself, with no redirect service in the middle that can expire, start charging or go down.