Out of the box, your Azure Web Apps don’t use browser caching to speed up the delivery of static content, to leverage browser caching simply add the below to your web.config’s <system.webServer> section, make sure the web.config is in your site’s wwwroot folder.

The lifetime of the cache is controlled using the cacheControlMaxAge parameter, the example above uses a lifetime of 7 days, this can be updated to reflect the lifetime you want to use.

Google recommends a minimum cache time of one week and preferably up to one year for static assets, or assets that change very infrequently.