1. Browser caching

In part 1, we looked at how it was possible to set an expiration header to any static file such as JavaScript and CSS files, so the browser would cache them for a long time and thereby optimize both for bandwidth and the number of requested files going from server to browser.

The problem with setting a browser cache expiration date of i.e. a JavaScript file to a year in the future becomes clear when you change the file before it expires in your visitor’s browsers. They simply won’t see the changes until they either clear their cache or hits F5 manually.

2. Bundle multiple files

Another common website performance issue is that there are many JavaScript and CSS files included on a page. This scenario results in the browser have to download a lot of extra files and that all slows down the performance of a website. The solution to this is also very simple when you’ve first completed the above steps to register the HTTP handler in web.config and called the BundleHelper.InsertFile method when inserting JavaScript and CSS files.

3. HTTP compression

You’ve always been able to perform HTTP compression in ASP.NET by using third-party libraries or own custom built ones. With IIS 7 you can now throw that away and utilize the build-in compression available from the web.config. Add the following line to enable HTTP compression:

<urlCompression doDynamicCompression=”true” doStaticCompression=”true” dynamicCompressionBeforeCache=”true”/>

By default, only text based content types are compressed.

4. Cache static files

To speed up the load time for the visitors, it is crucial that everything that can be cached by the browser IS cached by the browser. That includes static files such as images, stylesheets and script files. By letting the browser cache all these files means it doesn’t need to request them again for the duration of the cache period. That saves you and your visitors a lot of bandwidth and makes the page load faster. A well primed browser cache also triggers the load and DOMContentLoaded event sooner.

It’s worth noticing that the output caching respects file changes and therefore refreshes ever time changes are made to the JavaScript and CSS files tunnelled through this code.