Rails `allowed_redirect_hosts` Finally Fixed Subdomain Redirects

Oct 6, 2025 · 2 min read · The Problem Everyone Has You're building a multi-tenant SaaS with subdomains. User logs in at www.myapp.com, you redirect them to tenant1.myapp.com. Rails throws this at you: ActionController::Redirecting::UnsafeRedirectError: Unsafe redirect to "htt...