If you are thinking of speeding up your website, Google might be telling you the answer is to create a cookieless subdomain or domain. Well, that's easy for you to say. How to serve static content from a cookieless domain? More importantly, what is a cookieless subdomain?
Instead, you can consider a cookieless subdomain is a term to describe data transferring from one point to another (in this case, data movement from subdomain to domain) has no cookies attached. Indirectly, this boost the loading speed of your domain.
This is what Google explain in its own words:
Static content, such as images, JS and CSS files, don't need to be accompanied by cookies, as there is no user interaction with these resources. You can decrease request latency by serving static content from a domain that doesn't serve cookies. This technique is especially useful for pages referencing large volumes of rarely cached static content, such as frequently changing image thumbnails, or infrequently accessed image archives. We recommend this technique for any page that serves more than 5 static resources. (For pages that serve fewer resources than this, it's not worth the cost of setting up an extra domain.)
What does this means to you?
All static contents or data that are transferred with the accompanied by cookies. Though cookies are not needed for any transaction and do not serve any advantage, they will automatically be available for all data transfer. The only way to avoid such is when static contents are obtained from a cookieless site.
Static content + cookieless domain?
Serving static content or resources from a cookieless domain reduces the total size of requests made for a page. It is also important to note that there is no point setting up static subdomain for this matter if you are using a powerful web host or having very less page.
Now that we had gone through the relationship between cookieless subdomain and serving static content, let's explore the right way to serve the following static resources from a domain that doesn't set cookies.
When it comes to creating a cookieless subdomain, using a CNAME could be the easiest way of all (at least for me). This step is extremely easy to follow and after configurations, you can start serving static resources from a domain that doesn't set cookies.
This subdomain will serve as a CDN subdomain which is the key criteria to enable the process of serving static content from cookieless domain.
In order to create a proper cookieless subdomain, you have to ensure that when you are creating your subdomain, make sure it is pointing to your root directory instead of creating a secondary one. For example, my root directory is /public_html and thus, it should be pointed or directed to /public_html and not the default, /public_html/static.
Once you have done pointing the subdomain, head over to your DNS Zone Editor. At times, these might be labeled as Simple or Advanced DNS Zone Editor for several types of cPanel but they are all alike.
You would need to either create or modify the Name to your subdomain name and CNAME as your main domain. Of course, for the Type, you would need to select CNAME. You may start this by hitting the create button and if there is already a record, you just need to modify the settings to the above.
Still not sure? Let me explain to you, in other words. When you create the CNAME record you want to enter your static domain/subdomain as the label, name or an alias and your A record domain as the content or value. (The CNAME term, which stands for Canonical Name, actually refers to the domain you are mapping to, not the alias. The common practice of referring to the alias as the CNAME is in fact backwards.)
I could not emphasize how important this is but you must not skip this step no matter what. In WordPress, there are two common cookie-setters which are WordPress and Google Analytics. All you need is to do little changes in the configurations and you would be well on your way to a cookieless subdomain.
For WordPress, head over to your wp-config by login into your cPanel. Open it up and add this line to the file. If you are wondering where exactly you may place this file, you can place it at the bottom most of the script.
This is definitely a no-brainer but just to make sure, do remember to change your domain to your own domain name. After that, save the file and you are good to go!
For Google Analytics, all you need to do is to search for the specific code you had earlier placed in on your site and replace the code with the below one. For a quick tip, most Google Analytics code is kept close to the <body>.
_gaq.push( ['_setAccount', 'UA-xxxxxxx-1'], ['_setDomainName', 'www.yourdomain.com'], ['_trackPageview'] );
Again, change your domain as seen above to your own domain URL and save the file.
Important note: If you are using cloudflare or any type of Content Network Delivery (CDN), please get your hosting and CDN provider to verify on the CNAME. For example, using Cloudflare will give you an error when you are following the above guide in changing the CNAME. Basically, the hosting or CDN provider will give you a new A figure to place in.
Now, treat yourself to a bottle of beer for the hard work and congratulations. You had managed to create a cookieless subdomain from scratch. This is one of the cheapest (and fastest) way to create a cookieless subdomain when it comes to serving static content to improve your website speed.