Sign In with OpenRouter

Add OAuth login to any web app. Users authorize on OpenRouter and your app receives an API key — no client registration, no backend, no secrets. Works with any framework.

Live demo: openrouterteam.github.io/sign-in-with-openrouter

Decision Tree

OAuth PKCE Flow

No client ID or secret — the PKCE challenge is the only proof of identity.

Step 1: Generate verifier and challenge

code_verifier  = base64url(32 random bytes)
code_challenge = base64url(SHA-256(code_verifier))

• Use crypto.getRandomValues(new Uint8Array(32)) for the random bytes
• base64url encoding: standard base64, then replace + → -, / → _, strip trailing =
• Store code_verifier in sessionStorage (not localStorage) — so the verifier doesn't persist after the tab closes or leak to other tabs (security: the verifier is a one-time secret)

Step 2: Redirect to OpenRouter

https://openrouter.ai/auth?callback_url={url}&code_challenge={challenge}&code_challenge_method=S256

Step 3: Handle the redirect back

User returns to your callback_url with ?code= appended. Extract the code query parameter.

Important: Before processing ?code=, check that a code_verifier exists in sessionStorage. Other routes or third-party code might use ?code= query params for unrelated purposes — a hasOAuthCallbackPending() guard ensures you only consume codes that belong to your OAuth flow.

Step 4: Exchange code for API key

POST https://openrouter.ai/api/v1/auth/keys
Content-Type: application/json

{
  "code": "<code from query param>",
  "code_verifier": "<verifier from sessionStorage>",
  "code_challenge_method": "S256"
}

→ { "key": "sk-or-..." }

Remove the verifier from sessionStorage before or after the exchange.

Step 5: Store the key and clean up

• Store key in localStorage
• Clean the URL: history.replaceState({}, "", location.pathname) to remove ?code=
• Cross-tab sync: Listen for storage events on the API key's localStorage entry so other tabs update when the user signs in or out

Auth Module Reference

Drop-in module implementing the full PKCE flow. Reduces risk of getting base64url encoding, sessionStorage handling, or the key exchange wrong.

// lib/openrouter-auth.ts
const STORAGE_KEY = "openrouter_api_key";
const VERIFIER_KEY = "openrouter_code_verifier";

type AuthListener = () => void;
const listeners = new Set<AuthListener>();
export const onAuthChange = (fn: AuthListener) => { listeners.add(fn); return () => listeners.delete(fn); };
const notify = () => listeners.forEach((fn) => fn());

// Cross-tab sync: other tabs update when user signs in/out
if (typeof window !== "undefined") {
  window.addEventListener("storage", (e) => { if (e.key === STORAGE_KEY) notify(); });
}

export const getApiKey = (): string | null =>
  typeof window !== "undefined" ? localStorage.getItem(STORAGE_KEY) : null;

export const setApiKey = (key: string) => { localStorage.setItem(STORAGE_KEY, key); notify(); };
export const clearApiKey = () => { localStorage.removeItem(STORAGE_KEY); notify(); };

// Guard: only process ?code= if we initiated an OAuth flow in this tab
export const hasOAuthCallbackPending = (): boolean =>
  typeof window !== "undefined" && sessionStorage.getItem(VERIFIER_KEY) !== null;

function generateCodeVerifier(): string {
  const bytes = new Uint8Array(32);
  crypto.getRandomValues(bytes);
  return btoa(String.fromCharCode(...bytes))
    .replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

async function computeS256Challenge(verifier: string): Promise<string> {
  const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(verifier));
  return btoa(String.fromCharCode(...new Uint8Array(digest)))
    .replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

export async function initiateOAuth(callbackUrl?: string): Promise<void> {
  const verifier = generateCodeVerifier();
  sessionStorage.setItem(VERIFIER_KEY, verifier);
  const challenge = await computeS256Challenge(verifier);
  const url = callbackUrl ?? window.location.origin + window.location.pathname;
  window.location.href = `https://openrouter.ai/auth?${new URLSearchParams({
    callback_url: url, code_challenge: challenge, code_challenge_method: "S256",
  })}`;
}

export async function handleOAuthCallback(code: string): Promise<void> {
  const verifier = sessionStorage.getItem(VERIFIER_KEY);
  if (!verifier) throw new Error("Missing code verifier");
  sessionStorage.removeItem(VERIFIER_KEY);
  const res = await fetch("https://openrouter.ai/api/v1/auth/keys", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ code, code_verifier: verifier, code_challenge_method: "S256" }),
  });
  if (!res.ok) throw new Error(`Key exchange failed (${res.status})`);
  const { key } = await res.json();
  setApiKey(key);
}

Sign-in Button

Build a button component that calls initiateOAuth() on click. Include the OpenRouter logo and provide multiple visual variants.

OpenRouter Logo SVG

<svg viewBox="0 0 512 512" fill="currentColor" stroke="currentColor">
  <path d="M3 248.945C18 248.945 76 236 106 219C136 202 136 202 198 158C276.497 102.293 332 120.945 423 120.945" stroke-width="90"/>
  <path d="M511 121.5L357.25 210.268L357.25 32.7324L511 121.5Z"/>
  <path d="M0 249C15 249 73 261.945 103 278.945C133 295.945 133 295.945 195 339.945C273.497 395.652 329 377 420 377" stroke-width="90"/>
  <path d="M508 376.445L354.25 287.678L354.25 465.213L508 376.445Z"/>
</svg>

Variants (Tailwind)

Recommended classes for visual consistency with the reference implementation:

Sizes

All variants use: inline-flex items-center justify-center gap-2 font-medium transition-all cursor-pointer disabled:opacity-50

Show a loading indicator while the key exchange is in progress. Default label: "Sign in with OpenRouter".

Dark mode

For dark mode support, add dark variants: swap light backgrounds to dark (dark:bg-neutral-900 dark:text-white) and vice versa for branded/cta (dark:bg-white dark:text-neutral-900).

Using the API Key

const response = await fetch("https://openrouter.ai/api/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${apiKey}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "openai/gpt-4o-mini",
    messages: [{ role: "user", content: "Hello!" }],
  }),
});

For the type-safe SDK approach (callModel, streaming, tool use), see the openrouter-typescript-sdk skill.

Resources

• OAuth PKCE guide — full parameter reference and key management
• Live demo — interactive button playground
• OpenRouter TypeScript SDK — callModel pattern for completions and streaming