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Aggregation and Minification

When to Use

Production environments - always enable JavaScript aggregation for performance.

Decision

Drupal aggregates multiple JavaScript files into single bundle, minifies, and serves with far-future cache headers. Configure via Performance settings.

Pattern

Enable in settings (admin/config/development/performance): - "Aggregate JavaScript files" - ON (production) - Combines multiple JS files into fewer bundles - Reduces HTTP requests - Applies minification

Library configuration: 

feature:
  js:
    js/feature.js:
      preprocess: true    # Include in aggregation (default)
      minified: false     # Not pre-minified, aggregate will minify

Pre-minified external library: 

external:
  js:
    https://cdn.example.com/lib.min.js:
      type: external
      minified: true      # Skip minification
      preprocess: false   # Don't aggregate external

Testing aggregated JS: Always test with aggregation enabled before deployment.

Common Mistakes

  • preprocess: false on custom JS - WHY: Prevents aggregation, extra HTTP request per file
  • Minifying already-minified files - WHY: Wastes processing time, potential corruption
  • Not testing with aggregation - WHY: Works in dev, breaks in production
  • Disabling aggregation for debugging - WHY: Forget to re-enable, production performance suffers

See Also