Have you ever played “Name That Tune”? They used to have this show where they’d play music and you had to name that tune. One of the mini-games in the show was called “Bid-A-Note” where the host read a clue and the contestants would alternate bidding. “I can name that tune in X notes..” where X was a whole number, and the bids ended when one of the contestants challenged the other to “Name That Tune” (or if someone bid one or zero notes).
Well. I can crash a WordPress site with one plugin.
When people ask why their site is slow, sometimes my coworkers will say “It’s the plugins, right? He has 40 plugins!” and I’ll say “Maybe.” Then I look at what the plugins are, because it’s never the number of plugins, but their quality. Take a look at Jetpack, which is 33 plugins in one. Is that going to cause more or less overhead than if you had 33 separate plugins installed?
WordPress is wonderful and beautiful because you can use plugins to do absolutely anything. At the same time, that beauty is it’s downfall, because you can use plugins to do anything. There are over 32,000 active plugins in the WordPress plugin repository. There are probably 4000 or so that are delisted or disabled. There are around 3000 more plugins on just one popular WordPress theme and plugin site. We haven’t even started listing themes.
It’s a mathematical impossibility to test every possible plugin combination with every theme on every server on every host with every extra (like mod_pagespeed or CloudFlare) added on. It’s impractical to expect every combination to play nicely together, not because of any defectiveness in the code of the plugin or WordPress, but because of the reality that all of those things vary from place to place. We build out things to be flexible, after all.
I love the flexibility. I think it’s awesome. But at the same time, I worry about it when people complain their site is slow. There’s, very rarely, one perfect answer. Not even “Oh, he was hacked” is the answer to why a site is slow, though it can be. The answer is invariably in the combinations and permutations of what someone has done with their site, what the visitors do with it, and how they interact. A site that posts once a week is different than one that posts four times a day. A site with no comments is different than one with 30 per post. And the more of those little differences you factor in, the harder it gets to determine how many plugins is too much.
Maybe it’s your memory. One plugin may need more memory than another, but the combination of two may need more than either would individually! Sadly, it’s not something you’re going to know until you start studying your own site. There are cool tools like P3 Profiler which do a great job of giving you an idea as to what’s going on, but it’s not the whole picture. It can’t be. Just look at all the tools we list for performance testing and consider how many and varied the results are.
How many plugins are too many? However many it takes to kill your site.
Oh, the one plugin I can run to crash a site? It was BuddyPress and I was using PHP CGI. Once I changed it to a different flavor of PHP, the issue went away.