Common reasons for slow pages & how to fix them

Speed optimisation of your website pages can get very technical quite quickly but there are often relatively simple fixes that you can implement to speed up your website.

• Slow Network Time – This could indicate an issue with your DNS or a slow provider for one reason or another. You may want to consider using a premium DNS provider or if you are loading lots of resources from third party sites then delivering these from a single CDN may help improve this. Another benefit to the CDN is that they are often likely to have server closers to your users which can improve site speed.

• Slow Server Time – This could indicate that it is taking a long time to generate your pages on the server before sending them to your visitor. Often, you may be able to implement application caching so that the server remembers what to send to your next visitor when they request the same page within a certain amount of time.

• Slow Transfer Time – This is typically caused by large source code for your website or application. Common causes of this are if you include lots of inline CSS or JavaScript directly within your pages code rather than external files. You may also get a small speed boost here if you utilise a server configuration that utilises multiple edge locations around the world to bring the content geographically closer to your user.

• Slow DOM Processing Time – This is the amount of time it takes to parse the HTML returned from the server. Again, this can be caused by lots of inline CSS and JavaScript which in some cases may be unavoidable.

• Slow DOM Completion Time – This is the amount of time it takes to download and parse external resources like images, fonts, CSS and JavaScripts. If you use a lot of additional CSS or JavaScript files, it can help to combine their contents into a single CSS or JavaScript file, to avoid additional requests.

If you use lots of large media, it is important to upload appropriately sized media for the placement and make use of compression where possible. If you receive a lot of mobile visitors then responsive image source sets to match the displayed resolution can also make a big difference.

Another step that you can take that may help improve this metric is reviewing your caching headers to ensure that your content doesn’t have to be downloaded every time when it has already been downloaded. Following this theme you should also avoid downloading any unused assets unnecessarily as this will also increase your DOM completion time.

• Slow On Load Time – This could indicate that scripts on your website are slowing things down. Ensure that you aren’t using low quality plugins on your site and if you are using a Tag Manager, make sure you don’t have too many heavy scripts triggered by the Window Loaded event. Often advertising networking scripts are guilty here.

If you have a slow page and none of the above issues or solutions seem likely, there are many page speed testing tools, such as GT Metrix and Google Pagespeed Insights, that you can scan your site with to provide more specific recommendations for steps that will improve your site.