Redirect from actions in Svelte

Introduction

Redirecting from actions helps you send users to a new page after they submit a form or perform an action. It makes the app feel smooth and guides users where they need to go next.

After a user submits a login form, redirect them to their dashboard.

When a user creates a new post, send them to the post's page.

If a user deletes an item, redirect them back to the list view.

After a user updates their profile, redirect to the profile page.

Syntax

Svelte

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async ({ request }) => {
    // handle form data here
    throw redirect(303, '/new-url');
  }
};

Use throw redirect(statusCode, url) inside an action to redirect.

Status code 303 means 'See Other' and is commonly used after form submissions.

Examples

Redirects the user to '/home' after the action runs.

Svelte

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async () => {
    throw redirect(303, '/home');
  }
};

Redirects to a thank-you page after saving form data.

Svelte

import { redirect } from '@sveltejs/kit';

export const actions = {
  save: async ({ request }) => {
    const formData = await request.formData();
    // save data logic
    throw redirect(303, '/thank-you');
  }
};

Sample Program

This form asks for a name. When submitted, the action checks if the name is given. If yes, it redirects the user to '/welcome'. If not, it returns an error (not shown here for simplicity).

Svelte

<script lang="ts" context="module">
import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async ({ request }) => {
    const formData = await request.formData();
    const name = formData.get('name');
    // pretend to save the name
    if (!name) {
      return { error: 'Name is required' };
    }
    throw redirect(303, '/welcome');
  }
};
</script>

<form method="post">
  <label for="name">Name:</label>
  <input id="name" name="name" required />
  <button type="submit">Submit</button>
</form>

Important Notes

Always use throw redirect() inside actions to perform redirects.

Use status code 303 to tell the browser to use GET for the redirected page.

Redirects help avoid resubmitting forms if the user refreshes the page.

Summary

Redirects from actions guide users after form submissions or events.

Use throw redirect(status, url) inside the action function.

Status code 303 is standard for redirecting after POST requests.

Practice

1. What is the purpose of using throw redirect(status, url) inside a SvelteKit action?

easy

A. To display an error message on the same page

B. To send the user to a different page after the action completes

C. To stop the server from running

D. To reload the current page without changes

Solution

1. Step 1: Understand the role of redirect in actions

   The throw redirect(status, url) command is used to send the user to a new page after an action finishes, such as after submitting a form.

2. Step 2: Identify the effect of the redirect

   This redirect changes the browser location to the given URL, guiding the user to a different page.

3. Final Answer:

   To send the user to a different page after the action completes -> Option B

4. Quick Check:

   Redirect in action = send user to new page [OK]

Hint: Redirect sends user to a new page after action finishes [OK]

Common Mistakes:

• Thinking redirect stops the server
• Confusing redirect with showing errors
• Assuming redirect reloads the same page

2. Which of the following is the correct syntax to redirect to '/dashboard' with status 303 inside a SvelteKit action?

easy

A. redirect(303, '/dashboard');

B. return redirect(303, '/dashboard');

C. throw redirect(303, '/dashboard');

D. throw new Redirect(303, '/dashboard');

Solution

1. Step 1: Recall correct redirect usage in SvelteKit actions

   In SvelteKit, to redirect from an action, you must throw the redirect, not just call or return it.

2. Step 2: Match the exact syntax

   The correct syntax is throw redirect(status, url). So throw redirect(303, '/dashboard'); is correct.

3. Final Answer:

   throw redirect(303, '/dashboard'); -> Option C

4. Quick Check:

   Redirect syntax = throw redirect(status, url) [OK]

Hint: Always use 'throw redirect' inside actions for redirects [OK]

Common Mistakes:

• Using return instead of throw
• Calling redirect without throw
• Using 'new Redirect' which is invalid

3. Given this SvelteKit action code:

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async () => {
    throw redirect(303, '/success');
  }
};

What happens when the form using this action is submitted?

medium

A. The user stays on the same page and sees no change

B. The form submission fails silently without redirect

C. A runtime error occurs because redirect cannot be thrown

D. The user is redirected to '/success' with a 303 status

Solution

1. Step 1: Analyze the action code behavior

   The action throws redirect(303, '/success'), which instructs SvelteKit to send a redirect response with status 303 to '/success'.

2. Step 2: Understand the effect on form submission

   When the form submits, the browser receives the redirect and navigates to '/success'.

3. Final Answer:

   The user is redirected to '/success' with a 303 status -> Option D

4. Quick Check:

   Throw redirect = browser navigates to new URL [OK]

Hint: Throwing redirect sends user to new URL after form submit [OK]

Common Mistakes:

• Thinking redirect throws error instead of redirecting
• Assuming user stays on same page
• Confusing redirect with silent failure

4. Identify the error in this SvelteKit action code snippet:

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async () => {
    return redirect(303, '/home');
  }
};

medium

A. Using return instead of throw for redirect

B. Missing await before redirect call

C. Incorrect import path for redirect

D. Redirect status code 303 is invalid

Solution

1. Step 1: Check how redirect should be used in actions

   In SvelteKit, redirects inside actions must be thrown, not returned.

2. Step 2: Identify the mistake in the code

   The code uses return redirect(303, '/home'); which is incorrect; it should be throw redirect(303, '/home');.

3. Final Answer:

   Using return instead of throw for redirect -> Option A

4. Quick Check:

   Redirect must be thrown, not returned [OK]

Hint: Redirect inside actions must be thrown, not returned [OK]

Common Mistakes:

• Returning redirect instead of throwing
• Forgetting to import redirect
• Using wrong status codes

5. You want to redirect users to '/profile' after a successful POST form submission using a SvelteKit action. Which status code should you use with throw redirect(status, '/profile') to follow best practices?

hard

A. 303

B. 302

C. 307

D. 301

Solution

1. Step 1: Understand HTTP redirect status codes for POST

   After a POST request, the recommended redirect status is 303, which tells the browser to perform a GET request to the new URL.

2. Step 2: Match the correct status code for SvelteKit redirect

   Using throw redirect(303, '/profile') ensures proper redirect behavior after form submission.

3. Final Answer:

   303 -> Option A

4. Quick Check:

   POST redirect status = 303 [OK]

Hint: Use 303 status for redirect after POST form submission [OK]

Common Mistakes:

• Using 301 or 302 which may cause method issues
• Using 307 which preserves method but is less common
• Not specifying status code at all