rollup-preserve-directives is a Rollup plugin designed to retain crucial JavaScript directives, like 'use strict', during the bundling process. This ensures that these directives, often vital for correct execution or interpretation, are properly included in the final bundled output. By default, Rollup may strip these directives, but this plugin prevents that, guaranteeing code compatibility and intended behavior across different environments and interpreters. It simplifies maintaining code integrity when bundling with Rollup.