> ## Documentation Index
> Fetch the complete documentation index at: https://spreecommerce.org/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# 4.0 to 4.1

> This guide covers upgrading a 4.0 Spree application to Spree 4.1.

<Note>
  If you're on an older version than 4.0 please follow previous upgrade guides and perform those upgrades incrementally\*\*, eg.

  1. [upgrade 3.5 to 3.6](3.5-to-3.6)
  2. [upgrade 3.6 to 3.7](3.6-to-3.7)
  3. [upgrade 3.7 to 4.0](3.7-to-4.0)
</Note>

## Update gems

Run the following command to update your gems to 4.1:

```bash theme={"theme":"night-owl"}
bundle update
```

## Install missing migrations

```bash theme={"theme":"night-owl"}
rake railties:install:migrations
```

## Run migrations

```bash theme={"theme":"night-owl"}
rails db:migrate
```

## Storefront upgrade

You have two options:

1. Migrate to the new Storefront UI
2. Stay at the current UI

## Migrate to the new Storefront UI

Spree 4.1 comes with a completely new mobile-first ultra-fast Storefront powered by Turbolinks.

To replace your current frontend with the new Spree UI follow these steps:

1. In your project root directory run:

   ```bash theme={"theme":"night-owl"}
    rails g spree:frontend:copy_storefront
   ```

   **WARNING** this will overwrite your current project templates, it's required for the new UI, so if you'll be asked by the generator what to do please choose **A** to proceed

2. Next, you will need to copy over two files:
   * [spree\_storefront.rb](https://raw.githubusercontent.com/spree/spree/main/core/lib/generators/spree/install/templates/config/initializers/spree_storefront.rb) to `config/initializers/spree_storefront.rb`
   * [spree\_storefront.yml](https://raw.githubusercontent.com/spree/spree/main/core/lib/generators/spree/install/templates/config/spree_storefront.yml) to `config/spree_storefront.yml`

3. If you overwrote any `spree_frontend` [controllers](https://github.com/spree/spree/tree/master/frontend/app/controllers) you will need to either remove your local copies or move your custom logic to [decorators](/developer/customization#extending-controllers)

4. The same goes for [helpers](https://github.com/spree/spree/tree/master/frontend/app/helpers/spree)

5. You will also need to remove this line:

   ```javascript theme={"theme":"night-owl"}
    //= require spree/frontend/spree_auth
   ```

   from `vendor/assets/javascripts/spree/frontend.all.js` file

## Stay at the current UI

If you wish to not move to the new Storefront UI it's still an option. Just proceed with the steps described below.

1. Copy over all views from Spree 4.0

   Copy overviews from: [https://github.com/spree/spree/tree/4-0-stable/frontend/app/views](https://github.com/spree/spree/tree/4-0-stable/frontend/app/views) to your application views directory: `app/views`

   **WARNING** remember to not overwrite your customizations!

2. Copy over all Stylesheets from Spree 4.0

   Copy over stylesheets from: [https://github.com/spree/spree/tree/4-0-stable/frontend/app/assets/stylesheets](https://github.com/spree/spree/tree/4-0-stable/frontend/app/assets/stylesheets) to `app/stylesheets`

   **WARNING** remember to not overwrite your customizations!

3. Copy over all JavaScript from Spree 4.0

   Copy over stylesheets from: [https://github.com/spree/spree/tree/4-0-stable/frontend/app/assets/javascripts](https://github.com/spree/spree/tree/4-0-stable/frontend/app/assets/javascripts) to `app/javascripts`

   **WARNING** remember to not overwrite your customizations!

## Read the release notes

For information about changes contained within this release, please read the [4.1.0 Release Notes](https://github.com/spree/spree/releases/tag/v4.1.0).