Performance revisited – 3 easy steps to speed up your site

I decided to write a short follow up from the post from last week about the performance of this site, but framed more as a “how to quickly speed up my site”. Even if you can’t or don’t want to go down the line of changing themes (or writing your own), profiling plugins to find the fastest options, or changing hosting company, by spending 5 minutes installing these 3 plugins you can get a significant performance boost.

1. Squish those images

Images generally make up the bulk of the download weight of a site, especially in badly behaved themes. While WordPress does compress the smaller versions it creates when you upload a new one, and got better at it in version 4.5, a bit more can go a long way to speeding things up.

There are plenty of plugins to do this, both premium and free, and they fall into two camps technically – those who offload the processing to another server, and those that do it on your server. The big reason for using the external server type is to lower the resource use on yours or because yours doesn’t have the required libraries (normally cheap shared hosting). However most decent hosts will have no problems, and I prefer to keep things under my control when I can, so I’ve chosen to use Ewww Image Optimizer. Ewww has come out ahead in various comparisons but I’ll leave it to you to choose from the competition. Once you’ve installed it, any new images uploaded will be automatically optimised, both the full size originals and the smaller ones. There’s only one more step – head to Media -> Bulk Optimize and click on Start Optimizing. This will scan the media library and optimise everything previously uploaded. If your theme comes with built in images, you can also click Scan and Optimize which will catch those too.

Images squished, quick and easy – on to step 2.

2. Cache money business (to quote Mark Jacquith)

WordPress is built on PHP and a MySQL database. While the browser needs to be sent HTML files, on the server PHP is used to generate that HTML by reading information from the database. All this takes time, and also resources. When you have more concurrent visitors then the server uses more resources, which causes it to slow down, and eventually become unable to serve them. One way around this is to buy a bigger server, but a cheaper and easier solution exists – caching. Caching is the process of grabbing the HTML that PHP generates, and saving it for a set time. Instead of each visitor going to PHP and the database to generate the HMTL, it is sent to them directly saving both time and load on the server. After a chosen time, or a trigger like publishing a new post, the saved HTML is thrown away and a fresh copy created. This ensures visitors get an up to date version. The exact impact will depend on your site and server, but as an illustration I was running a load test on a client server last month: without caching the site became unresponsive after 36 concurrent visitors, with caching it was still going strong at 1500! NB – the site in question has some very complex pages making large numbers of database queries; also, these ‘users’ all doing indentical actions at exactly the same moments which would equate to a larger number of real-world users.

This was achieved using the popular free plugin WP Super Cache. Caching is more complicated than image optimisation, but WP Super Cache strikes a good balance between its simplicity and power. Even just installing the plugin and using the default settings on the Easy screen will give your site a huge boost. But it’s worth having a read of the Advanced and Preload tabs to refine things – the settings all have good inline documentation. For most turning on all the Recommended items on the Advanced screen is a good start, as well as reviewing the Expiry Time & Garbage Collection values (the text under the setting box has good examples).

Your site will now be both quicker and able to cope with more visitors. But there’s one more thing to do.

3. Minify, compress and concatenate HTML, CSS and JavaScript

Images squished, HTML pre-generated – but there’s also CSS and JavaScript being sent to users. Have a look at your site using View Source in your browser of choice. Since most themes are fairly badly behaved you’ll likely see multiple CSS and JavaScript files relating to the theme, and on top of that there will probably be ones added by plugins. Each separate file is both adding bytes to be downloaded, and also a connection that has to be opened from the browser to the server which takes time.

The solution to this threefold:

  • minification – remove spaces and rewrite files to shorten the length of them.
  • concatenation – join files together so that fewer have to be downloaded.
  • compression – server the files from the server with file compression to make them smaller, and send special headers to tell the browser to cache them locally to save downloading them again.

One plugin can so all this for us – Autoptimize. Install, activate, and turn on the 3 basic options to optimise HMTL, CSS and JavaScript. This one does need a bit more care – there is potential to break JavaScript code in particular. I’d recommend giving your site a good test after this basic activation to check everything is ok. If so, feel free to enable the Advanced Settings and tweak it to squeeze a bit more performance out – it’s all well documented. One advanced setting in particular to look at is inlining CSS. If your theme is quite a light one, inlining it all is best. If your theme is more complex, inlining ‘above the fold’ CSS will drastically improve the apparent loading speed of your site. This is because the browser will have enough information to render the visible area of the site even while it is still loading the rest.


5 Minutes, that all it will take – probably less time than it took to read this ramble – and you will have netted a substantial increase in performance. If you’re still after more speed things get a bit more complex – a faster server / host or a better theme would be the next on my list. Beyond that there’s object caching, server caching, CDNs, server optimisation, code optimisation… It goes on, but the 3 simple steps here should be all that 90% of sites need. To take things further I’d highly recommend reading this detailed article on WordPress performance and bottlenecks at Smashing Mag.

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