# v4 code migration: Updating theme customizations
This guide is part of the v4 code migration guide designed to help you migrate the code of a Strapi application from v3.6.x to v4.0.x.
🤓 v3/v4 comparison
In Strapi v3, theme customization was not supported.
Strapi v4 introduces the Strapi Design System (opens new window) with a brand new theme for the admin panel.
To customize the theme in Strapi v4:
- Rename the
./src/admin/app.example.js
file to./src/admin/app.js
. - In
./src/admin/app.js
, declare new key/value pairs in theconfig.theme
object, updating the design elements (e.g. colors, shadows, sizes) of the default theme (opens new window).
Example of theme customization in Strapi v4:
// path: ./src/admin/app.js
export default {
config: {
theme: {
colors, shadows, sizes, …
}
},
bootstrap() {},
};
💡 Customization tip
The Strapi Design System (opens new window) is fully customizable.