Connect React/Next.js apps to Encore.ts backends.
Encore provides tools to connect your frontend applications to your backend APIs.
# Generate client for local development
encore gen client --output=./frontend/src/client.ts --env=local
# Generate client for a deployed environment
encore gen client --output=./frontend/src/client.ts --env=staging
This generates a fully typed client based on your API definitions.
// frontend/src/client.ts is auto-generated
import Client from "./client";
const client = new Client("http://localhost:4000");
// Fully typed API calls
const user = await client.user.getUser({ id: "123" });
console.log(user.email);
const newUser = await client.user.createUser({
email: "[email protected]",
name: "New User",
});
// frontend/src/components/UserProfile.tsx
import { useState, useEffect } from "react";
import Client from "../client";
const client = new Client(import.meta.env.VITE_API_URL);
export function UserProfile({ userId }: { userId: string }) {
const [user, setUser] = useState(null);
const [loading, setLoading] = useState(true);
const [error, setError] = useState(null);
useEffect(() => {
client.user
.getUser({ id: userId })
.then(setUser)
.catch(setError)
.finally(() => setLoading(false));
}, [userId]);
if (loading) return <div>Loading...</div>;
if (error) return <div>Error: {error.message}</div>;
return (
<div>
<h1>{user.name}</h1>
<p>{user.email}</p>
</div>
);
}
import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
import Client from "../client";
const client = new Client(import.meta.env.VITE_API_URL);
export function UserProfile({ userId }: { userId: string }) {
const {
data: user,
isLoading,
error,
} = useQuery({
queryKey: ["user", userId],
queryFn: () => client.user.getUser({ id: userId }),
});
if (isLoading) return <div>Loading...</div>;
if (error) return <div>Error: {error.message}</div>;
return <div>{user.name}</div>;
}
export function CreateUserForm() {
const queryClient = useQueryClient();
const mutation = useMutation({
mutationFn: (data: { email: string; name: string }) =>
client.user.createUser(data),
onSuccess: () => {
queryClient.invalidateQueries({ queryKey: ["users"] });
},
});
const handleSubmit = (e: React.FormEvent<HTMLFormElement>) => {
e.preventDefault();
const formData = new FormData(e.currentTarget);
mutation.mutate({
email: formData.get("email") as string,
name: formData.get("name") as string,
});
};
return (
<form onSubmit={handleSubmit}>
<input name="email" type="email" required />
<input name="name" required />
<button type="submit" disabled={mutation.isPending}>
{mutation.isPending ? "Creating..." : "Create User"}
</button>
</form>
);
}
// app/users/[id]/page.tsx
import Client from "@/lib/client";
const client = new Client(process.env.API_URL);
export default async function UserPage({ params }: { params: { id: string } }) {
const user = await client.user.getUser({ id: params.id });
return (
<div>
<h1>{user.name}</h1>
<p>{user.email}</p>
</div>
);
}
Configure CORS in your encore.app file:
{
"id": "my-app",
"global_cors": {
"allow_origins_with_credentials": [
"http://localhost:3000",
"https://myapp.com",
"https://*.myapp.com"
]
}
}
| Option | Description |
|---|---|
allow_origins_without_credentials | Origins allowed for non-credentialed requests (default: ["*"]) |
allow_origins_with_credentials | Origins allowed for credentialed requests (cookies, auth headers) |
allow_headers | Additional request headers to allow |
expose_headers | Additional response headers to expose |
debug | Enable CORS debug logging |
For authenticated requests, pass the Authorization header:
// Using fetch
const response = await fetch("http://localhost:4000/profile", {
headers: {
Authorization: `Bearer ${token}`,
},
});
// Or include credentials for cookie-based auth
const response = await fetch("http://localhost:4000/profile", {
credentials: "include",
});
With TanStack Query, configure a default fetcher:
const queryClient = new QueryClient({
defaultOptions: {
queries: {
queryFn: async ({ queryKey }) => {
const response = await fetch(queryKey[0] as string, {
headers: { Authorization: `Bearer ${getToken()}` },
});
if (!response.ok) throw new Error("Request failed");
return response.json();
},
},
},
});
If you prefer not to use the generated client:
async function getUser(id: string) {
const response = await fetch(`http://localhost:4000/users/${id}`);
if (!response.ok) {
throw new Error(`HTTP error: ${response.status}`);
}
return response.json();
}
async function createUser(email: string, name: string) {
const response = await fetch("http://localhost:4000/users", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ email, name }),
});
if (!response.ok) {
throw new Error(`HTTP error: ${response.status}`);
}
return response.json();
}
# .env.local (Next.js)
NEXT_PUBLIC_API_URL=http://localhost:4000
# .env (Vite)
VITE_API_URL=http://localhost:4000
encore gen client to generate typed API clientsencore.app for production domainsallow_origins_with_credentials for authenticated requestsAuthorization header for token-based authcredentials: "include" for cookie-based auth