+page.server.js in SvelteKit: What It Is and How It Works

+page.server.js in SvelteKit is a special file used to run server-side code for a page, such as loading data or handling form actions securely. It runs only on the server, never in the browser, helping separate backend logic from frontend UI.

How It Works

Imagine your web page is like a restaurant. The +page.server.js file is the kitchen where all the cooking (data fetching and processing) happens behind the scenes. The customer (browser) only sees the finished dish (the rendered page) but never the kitchen itself.

In SvelteKit, +page.server.js runs only on the server. It can fetch data from databases, call APIs, or handle form submissions securely without exposing sensitive details to the user. This separation keeps your app safe and organized.

When a user visits a page, SvelteKit runs the code inside +page.server.js first to prepare the data. Then it sends the data to the frontend to display. This way, the page loads with all needed information ready.

Example

This example shows how +page.server.js loads data for a page and handles a form submission.

javascript

export async function load() {
  // Simulate fetching data from a database
  return { message: 'Hello from the server!' };
}

export const actions = {
  default: async ({ request }) => {
    const formData = await request.formData();
    const name = formData.get('name');
    return { success: true, greeting: `Hello, ${name}!` };
  }
};

Output

When the page loads, it shows: Hello from the server!
When the form is submitted with a name, it responds with: Hello, [name]!

When to Use

Use +page.server.js when you need to run code only on the server side for a specific page. This includes:

• Loading data securely from a database or private API before the page renders.
• Handling form submissions or other actions that require server processing.
• Keeping sensitive logic or secrets hidden from the browser.

For example, if you build a blog, you might fetch posts from a database in +page.server.js. Or if you have a contact form, you handle the submission there to send emails safely.

Key Points

• Runs only on the server: never exposed to the browser.
• Handles data loading: prepares data before page renders.
• Manages actions: processes form submissions or other server tasks.
• Improves security: keeps secrets and sensitive logic safe.
• Works per page: each page can have its own +page.server.js.

Key Takeaways

+page.server.js runs server-only code for a specific page in SvelteKit.

Use it to load data securely and handle form actions without exposing secrets.

It runs before the page renders, sending prepared data to the frontend.

Each page can have its own +page.server.js for isolated server logic.

Helps keep your app organized by separating backend and frontend code.