It’s commonly accepted that plugins slow down your WordPress install dramatically. They add extra resources, extra database calls, and lots of extra functionality – all of which adds to your loading time and slows down your site.
I’ve always wanted to test out exactly how much of a hit plugins add to a site and I recently got the chance to do a little un-scientific testing. The results are pretty amazing.
I started out with a fresh install of WordPress 3.6 and no content other than their few sample posts/pages. This is about as barebones as it gets and the site loaded in 1.86 seconds (all of these load times are from fresh Incognito windows in Google Chrome on a Mac) uncached and un-gzipped. This is a little slower than I’d prefer, but it will provide a good baseline for our testing.
Next, I added all of our normal-use and one-time use plugins WITHOUT activating them. Since none of them were active, it didn’t add any time to the loading speed of the site – simply gave us 76 plugins to play around with.
Next, I started activating plugins in groups of 10 at a time. Some of these groups included just add-ons for other plugins and most of the plugins weren’t configured which means they added no extra resources.
10 Plugins – 1.47 (oddly slower than the initial install)
20 Plugins – 1.45
30 Plugins – 2.07
40 Plugins – 3.24
50 Plugins – 1.99
60 Plugins – 3.18
70 Plugins – 3.32
76 Plugins – 6.13
Even without configuring a single plugin, the loading time quadrupled to over 6 seconds! Approximately 67 resources were being constantly loaded and this on a website that had no extra functionality. You’ll notice some anomalies within those numbers – this can be accounted for by certain plugins actually speeding up the site such as WP Super Cache or WP-Optimize.
The front end loading time wasn’t even the biggest issue. The admin section of the website was downright unusable with loading times hovering between 10 and 20 seconds on each page!
Also, keep in mind that we select plugins based on their resource intensiveness – in other words, we dump plugins that take up too much resources so all of our plugins should inherently perform excellently. Other plugins such as the popular NextGen gallery and certain plugin combinations will results in significantly slower loading times.
The lesson here is to use plugins only when absolutely necessary and run as few as possible. The commonly accepted number is less than 25 plugins on a site to keep it quick, but I like to keep it under 10 plugins for a regular small site. If you’re running an app or some sophisticated functionality on your site you’ll need some extra plugins, but try to keep them tame by using methods like killing the scripts and styles on pages where they’re not needed and use gzipping and caching to save resources.