Mojang has no public profile page — NameMC does
Minecraft doesn't give players a public web profile, so there's nothing on minecraft.net to link to. NameMC fills that gap: it shows the skin, cape and name history for any username, and it's the page the community already uses when someone asks "who is that?".
For servers, the more useful code points somewhere else entirely — your server's site, its Discord invite, or a voting page. Paste any of those through "Any link". A code on a spawn-area sign photo, a YouTube thumbnail or a merch tag does more work than a personal profile ever will.
One thing to know about usernames: when someone changes theirs, the old name is held for a period before anyone else can take it. A code pointing at a name you've abandoned may eventually show a different player, so regenerate after a change.
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.