Making WordPress Sites Faster - Caching & CDN's

Speed plays a big role in the life of any website, it can affect your search rankings but more importantly it can have a huge affect on user experience. Last year we did a ton of experiments and saw a massive 81.7% increase in speed of this website by swapping caching plugins and adding a CDN to the site, you can read about our website speed optimisation here.

Since then we've built on our experiences and rolled it out across most websites we manage, and of course recommended it as a course of action for any site which is looking to improve it's SEO.

But we are never happy with the same old results, things change - wordpress updates, plugins change etc. So this week we've been running a series of tests to further optimise the speed of the wordpress websites.

The Candidates for Improvement

We tested our changes across multiple websites, for the purpose of this article we will discuss only two - SEO Andy and Mick Cookson Photography.

We are looking at these because they sit on a server designed for speed, designed for wordpress and are always being optimised. This means they are in great condition generally and so it would be hard to improve them simply by changing one or two elements of the website.

What We Tested & Our Theory

Over the months we've tested lots of things from running images through "smushers" to reduce the filesize to attempting to reduce javascript calls etc.

However, for the purpose of our tests we wanted to do something that any website owner could do, quickly and easily - that doesn't involve web development.

So we settled on testing changing our Caching Plugin and the CDN we use.

Our theory was that by swapping to the plugin WP SuperCache (recommended by many wordpress expert websites) we would improve the speed.

Our second theory was that switching from CDN : MAXCDN to KeyCDN would help our page speed also.

How We Tested Our Speed

We decided on testing our theories to improve website speed using the below system... Note: we used page load time to quantify improvement.

  1. Benchmark Test the websites in their current state, using ManageWP Performance Test (this uses GTMetrix API)
  2. Switch the CDN to the new CDN, Test again.
  3. Switch WordPress Caching Plugin (from WP Rocket to WP SuperCache) - new benchmark
  4. Test with Existing CDN
  5. Switch CDN, Test again.

This was repeated for both websites, across multiple pages. The averages are recorded below.

We checked each site's cache was cleared between tests, the cache was preloaded before each test. We also checked each site was in working order, this meant testing SEO Andy without javascript via either CDN during testing.

Results: 33% Increase in Web Page Speed

On Mick's website during the test with WP Rocket we saw a 33.24% improvement compared with the benchmark. This improvement as shown below, with our other results, was a 2.38 second improvement on average.

As a Wedding Photographer in Manchester, Mick's site is hugely filled with images of his work. This makes the website fairly heavy in terms of loading requirements. This 33.24% increase in speed is pretty drastic and is actually something you can feel the difference before and after.

On SEO Andy the result was a 14.19% increase in speed, 0.403 seconds of improvement. Whilst not seeming significant time wise, this small difference is really important as part of the test - it validates that even websites such as SEO Andy which are optimised a lot can be improved through use of the new CDN, KeyCDN, and use of WP Rocket together.

The other result from this test was that the best free wordpress cache plugin we know of, WP SuperCache, was outperformed in both benchmarks and CDN tests - with WP Rocket surpassing it with ease in all tests.

The Outcome

Following the conclusive improvements to website speed, which was replicated across sites (with results from 10% to 35% improvement), it is clear that KeyCDN has an advantage over MaxCDN and the WP Rocket beats WP SuperCache.

This said, the improvements are not in the same scale as our previous test (75%), however this is because we are not testing against a benchmark of not using a Caching plugin or CDN - which would have caused a similar result as to last year.

Another note is that whilst MaxCDN is cost effective, KeyCDN is even more so - it's really pretty impressive.

We'll be re-running this test and expanding it in the coming weeks and months. If you have a suggestion for a wordpress cache plugin or CDN please leave a comment below.