# Connecting Users (Alias) By default Streak.dev tracks a **visitor-id** that lives in `localStorage`. When that same person signs in to your product you probably want their hard-earned streak to follow them to every device. This is done with **one extra request** to the `/alias` endpoint. The request links the current `visitorId` with your own **user ID**. 👉 **You only need to call `aliasUser()` once per visitor ⇄ user pair.** The operation is idempotent and duplicate calls are ignored. --- ## 1 Copy-paste integration (works in any site) ```html ``` If the page already knows the `USER_ID` when it renders you can skip the helper and just set `data-user` directly. --- ## 2 React / Next.js (with npm SDK) Install the tiny SDK: ```bash npm i @streakdev/sdk ``` Add a client component: ```tsx 'use client'; import { useEffect } from 'react'; import { aliasUser } from '@streakdev/sdk'; import { useSession } from 'next-auth/react'; export function StreakAlias({ projectId }: { projectId: string }) { const { data: session } = useSession(); const userId = session?.user?.id; useEffect(() => { if (!userId) return; const flag = `sd_alias_${userId}`; if (localStorage.getItem(flag)) return; aliasUser(projectId, userId) .catch(() => {}) .finally(() => { try { localStorage.setItem(flag, '1'); } catch {} }); }, [projectId, userId]); return null; } ``` Mount it once (e.g. in `app/layout.tsx`) **after** your auth provider: ```tsx ``` And remember to pass the user id to the widget when you can: ```tsx