HTTP status codes / 3xx — Redirection
301 Moved Permanently
What it means
The resource lives at a new URL forever; the Location header says where. Browsers cache this aggressively and search engines transfer ranking to the target.
What causes it
Domain migrations, http→https upgrades, URL restructures, www/apex canonicalization.
How to fix it
Landed somewhere odd? A stale cached 301 may be responsible — a cleared cache re-checks. Site owners: be certain before shipping a 301; browsers may remember it for months.