Core Library Definitions Now Support before and after Ordering in Drupal 11.5

Drupal 11.5 introduces Drupal 11.5 library ordering, a new feature that allows libraries to be loaded before or after another library without declaring a dependency. The new before and after keys make asset ordering cleaner, reduce unnecessary dependencies, and provide a more maintainable way to control JavaScript and CSS loading.

Previously, developers often added dependencies solely to influence load order, even when the libraries were otherwise unrelated. This could result in additional assets being loaded unnecessarily.

Drupal 11.5 Library Ordering

The new before and after properties can be added directly to a library definition.

Example

before_main:
  js:
    before_main.js: {}
  before:
    - common_test/main

main:
  js:
    main.js: {}

after_main:
  js:
    after_main.js: {}
  after:
    - common_test/main

In this example:

• before_main always loads before common_test/main
• after_main always loads after common_test/main
• no dependency relationship is created

Why This Matters

Previously, controlling library order often meant adding something like:

dependencies:
  - common_test/main

even when the library didn't actually require it.

This caused Drupal to load additional libraries simply to satisfy dependency resolution.

With the new ordering API:

• asset order is explicit
• unrelated dependencies are avoided
• fewer unnecessary assets are loaded
• library definitions are easier to understand

Replacing File Weights

Many themes and modules have historically relied on file weights.

Example:

js:
  js/custom.js:
    weight: 100

Drupal now recommends using before and after instead.

Custom file weights are discouraged and may be deprecated in a future Drupal release.

When to Use before and after

Use these keys when:

• extending a contributed library
• overriding JavaScript behavior
• ensuring initialization scripts run in the correct order
• integrating third-party JavaScript
• organizing frontend assets in themes

Do not use them when one library genuinely depends on another. In those cases, continue using dependencies.

Benefits

The new feature provides several advantages:

• cleaner library definitions
• fewer artificial dependencies
• improved maintainability
• more predictable asset loading
• better frontend architecture

Migration Tips

When upgrading to Drupal 11.5:

• Review library definitions that use dependencies only for ordering.
• Replace those dependency declarations with before or after where appropriate.
• Audit custom file weights and migrate to the new ordering mechanism when possible.
• Keep true dependencies unchanged.

Final Thoughts

The introduction of before and after in Drupal 11.5 is a welcome improvement to the Libraries API. It separates asset ordering from dependency management, resulting in cleaner code and more efficient library loading. As Drupal continues to modernize its frontend architecture, adopting this feature will help keep modules and themes easier to maintain.

Official Change Record:
Core library definitions support before/after ordering