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WordPress Cache: How It Works at Application- and Server-level

Updated on December 21, 2021

7 Min Read
wordpress cache

On Cloudways blog, I frequently cover topics around WordPress optimization and recently Cloudways also hosted WordPress performance contest in which contestants were challenged to speed up a WordPress site. The winner of the contest applied various optimization techniques among which caching played an important role.  

If you wish to achieve true website optimization, you can not neglect the role of WordPress cache. Just a few years ago, caching was little-known in the WordPress community. Today, it is a hot topic in WordPress community discussions. Website owners are able to achieve a high level of performance by properly applying WordPress cache optimization tactics. 

However, many in the community still don’t know much about cache optimization. This article is for all such users. To give you all some details about how to cache optimization works, I have broken down this article in server-level caching and client-side caching.

What Is Caching?

Caching is the term used for storing and reusing the assets elements to save server resources and offer better user experience. WordPress cache allows you to serve web content fast while keeping the server available to handle other requests.

A typical example of caching is the Page Cache (explained later). Page Cache keeps a copy of the web page and displays it when a user requests it. This saves a trip to the website backend and database to fetch page content again. So basically, WordPress cache simply helps your server maintain the balance between the available resources and the user requests by serving the already saved data to the user.

Benefits of Caching

Applying cache to your WordPress site offers a host of benefits including:

  • Faster loading webpages.
  • Improved SERP ranking as Google prefers fast websites.
  • Better server resource management.
  • Enhanced user experience.
  • Better traffic handling.

Server-Level Caching

Caching in WordPress can be applied primarily at the server level and application level. In this section on server-level caching, I will introduce the caching mechanism on a server which is further broken down into the following:

Varnish – Reverse Proxy

Varnish caching is a great way of speeding the website load time by as much as 10x. It is a reverse HTTP proxy that acts as a middleman between the server and the clients. It caches the content after the initial request and serves the copy to subsequent requests.

Varnish - Reverse Proxy

Source: wp-rocket

Varnish cache takes caching to a whole new level by making the PHP web server 100x more efficient unlike caching plugins that can start to show the strain of the increasing number of requests. Varnish can be used to cache both dynamic and static content and can help you boost website and server performance.

Page Cache

Page Cache also is known as site cache store data such as web pages, images, and other media content on the server. This stored data is then quickly served to the users requesting the same page. Page Cache maintains a memory reference that is triggered when the server receives a request for a page that has already been served before. Instead of going back to the backend and database to fetch the data for the request, the data is served from this cache.

This cached content can be controlled from the user’s browser. For example, users can set an expiry for the content depending upon the nature of the content. After the expiry date, the content is cleared and is replaced with the new and updated content.

Redis – Database Caching

Redis is an amazing tool used for object caching and/or database caching. It caches database queries to optimize the overall website performance. Redis is a great open-source option that supports a wide range of data structures and can store data in-memory for faster processing.

When the user launches a request, this request is taken to the website backend where the PHP code process it, and if needed, generates and executes a database query to fetch data from the tables. This back and forth takes time which can be avoided by using Redis caching.

Memcached – Object Caching

Memcached is another great open-source tool that can also cache database queries. It has an in-memory key-value storage process that speeds up dynamic web applications by optimizing data fetch time.

Dynamic websites such as eCommerce stores can benefit from Memcached by reducing the load on the database. Memcached processes redundant requests faster by eliminating the whole process of going to the website backend and querying database tables for data items.

Opcode Caching

Opcode Caching is an efficient way to cache the already processed PHP code between the requests. Opcode caching saves the converted bytecode in memory so that it can be served instantly for the subsequent requests.

Opcode Caching

PHP versions 5.5 and later are shipped with Opcode caching. Opcode caching improves the speed and helps the server handle more unique requests in a given time.

CDN Cache

Content Delivery Network (CDN) is a geographically dispersed service that serves a copy of the website from multiple locations. CDN reduces the latency by serving the webpage data from the nearest node to the end-user.

CDN can serve both the static and dynamic data and saves the bandwidth of the server. Another important benefit of CDN services is an improvement in website security as it is very difficult to pinpoint the actual location of the server/website.

Application-Level Caching

Client-side cache or application-level cache involves browser caching that can be implemented using WordPress plugins.

Browser Caching

A typical WordPress site contains images, CSS and JavaScript files. These resources are rendered by the user’s browser to display the page content. By leveraging browser cache for WordPress, the website you can cache this static data inside your web browser for future usage.

Almost all major web browsers have built-in capabilities to manage browser cache. The browser generally stores these files in the local storage, and thus it is highly recommended to clear browser cache periodically.

Now, let’s look at some of the WordPress cache plugins.

WordPress Caching Plugins

WordPress cache plugins are a great way of optimizing your WordPress site for performance. There are various plugins out there but in this article, I try to cover some of the best WordPress cache plugins.

1) Breeze


Breeze is a free cache plugin developed by Cloudways. It is a simple yet effective WordPress cache plugin. Breeze offers all the major features useful for application-level caching and minification & grouping of CSS and JS files.

2) Hummingbird Page Speed Optimization

Hummingbird Page Speed Optimization

Hummingbird is considered as one of the best WordPress cache plugins developed by WPMU DEV. The plugin has over 70,000 active installations and offers features like compression, minification, lazy loading, and browser caching tools.

3) W3 Total Cache

W3 Total Cache

W3 Total Cache plugin offers key features like AMP support, SSL support, CDN management for media, and database object caching. It is among the more popular WordPress cache plugins with over a million active installations.

The above plugins are considered as best WordPress cache plugins. Try any of these but be sure to backup your WordPress site before implementing any level of caching.

4) WP Rocket

WP Rocket is one of the best performance plugins for WordPress. It will reduce your loading time in a few clicks. Thanks to its powerful performance features, you’ll boost your Google PageSpeed and Core Web Vitals scores with no effort.

Clear Cache in WordPress

Purging or clearing cache in WordPress is as important as setting up a cache at your WordPress site. Clearing cache should be a frequent practice especially when you make changes to files. This ensures users get the updated content. If you are using the Breeze WordPress cache plugin, you can clear the cache simply from the plugin settings.

Clear Cache in WordPress

Cloudways Takes Care of Everything!

If you are a Cloudways customer you do not have to worry about server-level caching. Cloudways optimizes the servers with an advanced caching mechanism to ensure optimum performance and availability.

Websites hosted on our optimized servers load as fast as 79ms! Cloudways customers can manage these caching services directly from their dashboard.

Cloudways WordPress cache

As shown in the above screenshot, users can restart, disable, and purge the cache in just a click. Isn’t that amazing?

Wrapping up!

WordPress cache is crucial for the performance of your website. If done properly, you can unlock a whole new level of user experience, SEO, and revenue just by optimizing your WordPress site for performance. However, before applying any technique mentioned in this tutorial, do remember to take a full backup of your site.

Q. What is a cache on WordPress?

Caching is the technique used to serve pre-loaded information to the user to avoid fetching the same information over and over again from the server. This reduces the load time and number of requests

Q. Where is WordPress cache stored?

It depends upon the type of cache. When you use WordPress cache for browser; the cached files are usually stored inside your web browser’s directory.

Q. How do I enable caching in WordPress?

WordPress cache can be enabled in various ways. One of the popular ways is to use a caching plugin.

Q. Should I delete cache WordPress?

Deleting WordPress cache from time to time can help in optimizing the resources. After a while, cached folders become large in size and can occupy more useful space.

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Ibad Ur Rehman

Ibad Ur Rehman is a WordPress Community Manager at Cloudways. He likes to explore the latest open-source technologies and to interact with different communities. In his free time, he likes to read, watch a series or fly his favorite Cessna 172SP in X Plane 11 flight simulator.


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