Mu-plugins

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Mustuse plugins (a.k.a. mu-plugins) are plugins installed in a special directory inside the content folder and which are automatically enabled on all sites in the installation. Must-use plugins do not show in the default list of plugins on the Plugins page of wp-admin (although they do appear in a special Must-Use section) and cannot be disabled except by removing the plugin file from the must-use directory, which is found in wp-content/mu-plugins by default. For web hosts, mu-plugins are commonly used to add support for host-specific features, especially those where their absence could break the site.

Despite its suitability for many special cases, the mu-plugins system is not always ideal and has several downsides that make it inappropriate in certain circumstances. Below are several important caveats to keep in mind:

The code handling /mu-plugins/ was merged into the main WordPress code on 03/07/09 with this changeset a full 10 months before the wpmu codebase was initially merged, and all WP sites could take advantage of autoloaded plugins, whether they had MU/Multisite enabled or not. The feature is useful for all types of WP installations depending on circumstances, so this makes sense.

I have my local WordPress setup I create folder named mu-plugins in wp-content/plugins/mu-plugins and in mu-plugins directory I create one file and write a simple code for test my mu-plugins not work it give no response.

Note that mu-plugins is not the same as plugin folder, but rather a place that you can put arbitrary PHP files that are all loaded. Files in subfolders are not loaded, and files are not scanned for plugin headers. E.g. if you copy a plugin folder into wp-content/mu-plugins it will not run as it's in a sub-folder.

Possibly because your host uses a non-standard custom location that serves the same purpose. It's very likely that there is a wp-content/mu-plugins folder on your host that contains host specific code, and that host specific code is then implementing a custom folder so that clients can still use mu-plugins.

For example, sites hosted on WPVIP Go don't have an mu-plugins folder because their Go platform code lives there. Instead customers use client-mu-plugins for the same purpose, but that wouldn't work on other hosts. Your host probably does the same.

Note: WordPress only looks for PHP files right inside the mu-plugins directory, and (unlike for normal plugins) not for files in subdirectories. You may want to create a proxy PHP loader file inside the mu-plugins directory:

Warning: We strongly recommend performing a complete backup of your site before changing things or adding code to server files in case anything goes wrong. Snapshot makes backing up and restoring WordPress sites a breeze!

Sticking with Elementor for this example, you may decide to hide this to avoid problems and leave the theme customization path inside the admin area at Templates > Theme Builder. Or you may decide to remove it altogether, because even if you disable options from the admin bar, some users may still not understand what it is and why it displays on the front end of their sites.

Note: You can use the previous step to hide the Elementor templates only (to keep your theme safe) but still leave access in Elementor to create and modify pages. This, however, can be risky, since when users are on an Elementor page, they can navigate to other elements like the header or footer, or access Elementor global settings that will affect the site.

Again, you can use Branda to customize the admin panel and the left menu or hide/show menus depending on the user role. This is great if you are the only admin and want to display the minimum required menus for end users or add custom CSS.

A MU plugin, also known as a must-use plugin, is a plugin that is installed in the /wp-content/mu-plugins/ directory of WordPress. Typically MU plugins, if they are present, are activated and cannot be deactivated, unless you manually remove them. Usually they are used to perform specific actions or add features on all sites in a multisite installation, like adding custom code or changing global settings of WordPress.

MU plugins in WordPress can be used in single site installations. These are typically done with web hosts that require sites to have features that work well with their setup, like caching and security. For example, some web hosts add the Limited Login Attempts to the MU Plugins folder and do not allow users to manually remove the plugin from their WordPress installation. The Limit Login plugin helps with stopping bot attacks from gaining access to the WordPress admin or overwhelming the site from tons of login attempts (also known as a brute force attack.)

MU plugins cleverly help improve the performance of WordPress websites, especially in multisite networks, because they only load once. And yes, they still load once if several sites on that network have it activated.

To install an MU plugin, you can use a FTP client. Below is a short step-by-step guide on how to do that. Please note that if you use cPanel through your web host, you can use the File Manager to also manually install a MU plugin in WordPress.

MU plugins in WordPress can be a cleverly powerful tool to not just manage many sites within a multisite network because it can efficiently help with performance. If you install MU plugins, make sure to use best practices within this article to keep your WordPress sites running smoothly.

Hi,

I want to install it on a multisite. The plugin should be available to all websites so I guess that I have a choice between activating the plugin for the network or putting it in the mu-plugins folder. But what will be the difference? Or is it equal to my situation?

I would suggest using Network Activation. If you are running it in multi-site I would also suggest pre-populating your license key for new sites that are created in multi-site by adding code to your wp-config.php file.

What this will do is pre-populate the license key on the settings page so you don't have to do it for each site. Just keep in mind it will only do this when a site is first created, so existing sites won't be pre-populated.

No idea why off the top of my head other than not implementing the code properly. It should work. Others are using it, as are we. Make sure the key is correct int he code is added properly in the wp-config.php file. What exactly do you mean by "crashes it", do you receive an error?

Must-Use (MU) plugins stand as the vanguards of WordPress customization, offering a level of control and flexibility that goes beyond the conventional. This comprehensive guide aims to delve even deeper into the world of Must-Use plugins, shedding light on their intricacies and showcasing the potential for customizing WordPress.

With a specific emphasis our own WordPress Must-Use plugin (often referred to in the industry as mu-plugins), let's navigate the landscape of WordPress customization and understand how these plugins can be harnessed to transform your website.

At their core, Must-Use plugins play a pivotal role in shaping the WordPress environment. Being immune to deactivation by site administrators, they execute before regular plugins, making them indispensable for implementing site-wide modifications. The early loading advantage allows developers to exert control over critical aspects of WordPress, influencing the core functionality and ensuring a tailored user experience.

For Nexcess customers, the Nexcess (NX) Managed Applications (MAPPS) Must-Use (MU) plugin is a familiar companion. Pre-installed to enhance the experience of customizing WordPress sites, it brings features like telemetry tracking, Object Cache Pro integration, and the Visual Compare feature. However, it's essential to note that opting out of the NX MAPPS MU plugin necessitates a flexible cloud hosting plan, striking a balance between customization freedom and the integrated features offered by managed WordPress plans at our company.

Beyond the confines of pre-installed plugins, users can embark on a journey of customization by developing their Must-Use plugins. Insights from the Nexcess Product Team emphasize the need for a strategic approach.

Understanding filters, actions, and hooks is crucial to effectively wield Must-Use plugins. Renaming the main PHP file in the mu-plugins folder provides an avenue for site-specific customizations. This level of control empowers developers to shape their WordPress environment, aligning it with their website's unique needs and objectives.

Using filters, actions, and hooks in your Must-Use plugin, allows you to customize other plugins, features, and settings without modifying their original code directly. This approach allows for easier updates of the original plugins in the future.

It's crucial to explore advanced techniques and use cases for customizing WordPress. Embracing this journey of learning will enable you to harness the full potential of Must-Use plugins in the context of the world of WordPress.

For Nexcess customers, the relationship between Must-Use plugins and the hosting environment opens up unique opportunities for optimization and customization. Here are specific considerations for leveraging Must-Use plugins in conjunction with your Nexcess hosting plan:

In conclusion, the realm of WordPress customization is enriched by the dynamic capabilities of Must-Use plugins. Whether leveraging the pre-installed NX MAPPS MU plugin or crafting your own, the key lies in understanding the intricacies of Must-Use plugins and how they can elevate your WordPress experience.

For Nexcess customers, choosing between managed WordPress plans and flexible cloud plans becomes a strategic decision. Managed plans offer the convenience of the pre-installed NX MAPPS MU plugin, ensuring a seamless and feature-rich experience.

Conversely, flexible cloud plans provide more control over Must-Use plugins, enabling a tailored approach to WordPress customization. For any additional information, Nexcess offers a rich knowledge base with related topics such as those covered in the Nexcess hosting and Nexcess Client Portal guide.

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