Which HTTP header is crucial for implementing a cache-first strategy in service workers?

Implementing a cache-first strategy in service workers requires the use of the Cache-Control HTTP header with directives like public and max-age. By specifying public, you allow the response to be cached, and max-age sets the maximum time that the response should be considered fresh. This strategy ensures that the service worker prioritizes cached responses over network requests when possible, enhancing performance and offline capabilities.