Since version 3.0 WordPress includes the feature to be turned into a multisite network. It can hold as many separate sites with their own WordPress dashboards as you need. They all use the same WordPress installation, the same database, and the same main folder.
This kind of setup offers many benefits, and could save you a lot of time, but it also comes with a lot of downsides. Let’s take a look at the main pros and cons of switching to a WordPress multisite.
Install Only Once
No more installing WordPress and setting up databases for new sites. There is one installation and one database for all sites. And since the plugins and themes are global, they also are installed only once and are ready to be used on new sites. Creating a new empty WordPress site takes seconds now.
This is one of the major benefits of a multisite. If you install a plugin that lets you clone existing sites, with just a few clicks you can duplicate a whole site and then start changing it according to the new project.
Update Only One Installation
One WordPress installation also means updating the core, the plugins, and the themes is done globally. The more sites you have, the more time this saves you.
Not having to log-in to every dashboard and go through the updating process of each plugin or theme for dozens (or hundreds) of sites, is really a major benefit. It is honestly one of the best things about a WordPress Multisite network.
The users in the multisite are also global and can easily be assigned a role for a given site. A user can be a subscriber in one site, an administrator in another, and have no role in the other sites. Your authors and editors now need only one account to log-in to all your sites.
There is also a Super Administrator role, which gives full access to all sites and access to the Network Admin Screen.
Less Server Space Used
Since the WordPress core, plugin, and theme files exist globally on one place only, this saves server space. However it leads to some downsides too, which we will cover below.
User Site Creation
In a multisite you can allow users to create new sites. This can turn your site into something like WordPress.com (don’t expect all the features they have though). This is not really something that helps you manage your sites, it is just a new feature that you cannot use without a multisite.
Save Money on Some Plugin Licenses
Some premium plugins will require you to buy only one license for an entire multisite, which can pretty much hold as many sites as you want. This will save you a lot of money, compared to buying a license for each site. Such a plugin is the very popular security plugin WordFence.
Of course, many plugins will still require a separate license for each site even if you use a multisite.
Migrating to a Multisite is a Nuisance
Creating a multisite from one site is not that hard, but if you want to migrate your current sites to a multisite, it could get very messy. Trying to put multiple sites with all kinds of themes and plugins all in one installation could pretty much make you give up the whole multisite idea
It will be a lot of work and most likely will require some changes to some sites. Some plugins may not even work properly in a multisite environment. And you have to test everything too, since many plugin authors don’t even know if their plugin will work well in a multisite. More about plugins below.
Moving a Site is Nuisance
Once you have moved all your sites in the multisite, the opposite process is also not that easy. If one of your clients wants to move out from the multisite or you sell one of your sites, you will need to separate that site somehow.
There is no folder for each site you can just archive, since the plugins and themes are global. And there is no one database you can just export, since it is global too. This makes the whole process pretty annoying and messy.
A single problem with the WordPress installation or with your server can cause all your sites to not work properly. Just one of the downsides of everything being in one place.
If a hacker finds out your Super Administrator credentials he can control all your sites.
Less Plugins Available
This is probably the biggest downside for me. Not all plugins work with a multisite, and there is not even a sure way of knowing which ones work and which don’t.
The best thing about WordPress is the free access to a large amount of all kinds of useful plugins. Unfortunately most of them are not tested in a multisite environment. Some highly popular plugins with hundreds of thousands of downloads just plainly say that they do not support WordPress multisite.
However, it is not required for the plugin author to even know about multisite – his plugin might work well in a multisite on its own. In many ways the multisite is the same as a normal WordPress site. In some ways, it is very different though.
There are also some plugins that work only with a multisite. They are specially made for it. So you get access to some new plugins too, but they are not that many at all.
Editing a Plugin or a Theme Affects All Sites
Since the plugin and theme files are global and exist only on one place on the server, if you edit some of them, this will affect all sites that use them. Usually editing these files is a bad idea anyway, because when you update the plugin (or theme) you will lose the changes, but sometimes there is no other way.
For themes you can kind of avoid this problem with a child theme. For plugins you can try to make another plugin that modifies the behavior of the plugin. However, most plugins are not really made to be modifiable this way.
Site Administrators Cannot Install Plugins or Themes
Only the Super Administrator can install or delete plugins and themes. Site administrators have to use the ones that are available in the multisite network.
One Big Database
Since all sites in the network use one database, this means that it will be much bigger in size and in number of tables. This could become a problem if you have a lot of sites.
Your hosting provider may have a limit on the number of database tables in a database, and also a limit on the total size of the database. Not to mention that a very big database may have performance issues.
Each new site will add at least 10 more database tables. Depending on the plugins that are active on the site, this number can be doubled, or even tripled.
Less Help Available
One more downside, of using something that is less popular, is that less people understand it. This means that when you ask for help on forums or when you want to hire a developer to do some task, less people will be available. Most people just don’t have any experience with WordPress multisite.
Some Themes Will Not Work
Almost all themes will work fine, even if their authors have never heard of WordPress multisite. Seriously, I have only seen one theme so far that has a problem with it.
The theme that had a problem was generating a CSS file based on its settings, and this file was stored in the theme folder. Since the theme folder is the same for each site in the network, this caused every site to use the same theme settings.
Icons taken from Flaticon.com