To maintain compatibility with both ECMAScript Modules (ESM) and CommonJS (CJS), it is crucial to use a dual-compatible approach, avoiding the "type: module" declaration in package.json files, and using the main and module fields correctly. The main field should point to a CJS export and the module field to an ESM export, allowing both types of consumers to access the package without additional configuration. Additionally, the exports field provides granular control over how the package is consumed, enabling developers to specify entry points for require() and import statements. For TypeScript projects, integrating package manifest exports with a module type ensures compatibility and type safety. By following these best practices, developers can create modern npm packages that are compatible with both ESM and CJS, ensuring wider adoption and integration across different projects.