Source: https://www.todhost.com/blog/web-hosting-tips/94-how-a-plugin-installation-can-crash-your-wordpress-website

WordPress plugins are used to add functionality to WordPress websites. But just as they can be a great way to improve the power of any website, they can also create problems for an existing website. Installing plugins should therefore be done with care in order not to cause problems especially for well established websites with huge content. Imagine losing a website you have built for 10+ years with over 10,000 articles simply because of a bad plugin you were installing. That is huge cost and will definitely impact traffic and rankings negatively. In this post, we examine why a plugin installation can be a problem for a WordPress website and how to prevent such problem. But what if the problem occurs, what should be done to rectify the damage? All of these are addressed in this post.

First, let us begin with an understanding of what WordPress plugins really are.

What Are WordPress Plugins and Why Do We Need Them?

A plugin is a piece of software containing a group of functions that can be added to a WordPress website. Essentially therefore, what plugins do is to extend the functionality of your WordPress website. The use of plugins have been very helpful for WordPress users especially beginners without any coding experience because a plugin just implements the functionality without creating any problems. Wait, did I say any problems? Well, the fact is that ordinarily, well coded plugins will not create problems. Unfortunately, not all plugins are well coded and so there could actually be problems associated with the use of some plugins.

Generally speaking, the following reasons justify the use of plugins on a WordPress website:

A plugin will help you use your WordPress website beyond its blogging capability. WordPress is basically a blogging platform. That is what it was originally developed to do. But with plugins, you can use it to set up your corporate website, build your social network, run a forum or community platform, create a business directory and even add e-commerce functionality. The potential for your WordPress website can be limitless with plugins and there are thousands of plugins available in the WordPress directory.
Plugins support the work of non-coders. WordPress is built on codes as you may already know. But most WordPress users do not know how to write codes. If they do, their coding capacity may not be advance enough to develop applications like plugins. So with plugins, it has become easy for everyone to work with WordPress and come up with very fascinating websites.
Plugins help developers save money. WordPress as you know is not so complex, not very advanced and do not offer a complex functionality to which it has been put today through the use of plugins. For you to have more functionality for your WordPress website, you need to do the coding yourself or hire someone else to do it for you which would have been quite expensive. With plugins, most of which come free, you are able to improve on the functionality of your WordPress website without spending additional fee in most cases.

As mentioned above, most WordPress plugins are free. There could be a paid version which allows more functionality but in most cases, the basic use for the plugin can be put allows you to have it free. This creates the temptation of installing as many plugin as possible. Installing as many plugin as you can have is not a problem but is actually unnecessary. This takes us to the question of which plugins to install:

Which WordPress Plugin Should I Install?

Your decision to install a WordPress plugin should depend on your research and answers to the following questions:

When last was the plugin updated?
Is the plugin compatible with the version of WordPress you are running?
Is there any technical support for users?
What comments are people making about the plugin based on their experience?

We will now attempt to explain how and why answers to this questions are important in the decision to install any WordPress plugin on any website.

Effect of Plugin Update on Your Website

According to Sucuri, most WordPress hacks occur due to failure to update plugins. Generally, you also will find that WordPress hacs are also caused by failure to update WordPress core and themes. But our focus here is on the plugins. WordPress itself warns against plugins that has not undergone any update in 2 years and will remove such plugin from its repository. When you fail to check a plugin status and update accordingly, you run the following risk:

the plugin itself could have been updated by the developer
the plugin could no longer be compatible with current WordPress version
A bug could have been fixed in old plugin making a new one available.

So you can see that checking for plugin update is very important not just for your website improved performance but also for its security. Now there are a couple of things to do before you ever embark on any kind of update on your WordPress website or any other.

Ensure you have a safe backup. This is extremely important and may be the best decision you ever too if there be a disaster and you are unable to find a fix. The one thing you can do is to return your website to an earlier date. At least from there, you can start all over again.
Preserve any modifications: You could have had some custom coding, we have a lot running on the site we build. You will have to preserve them so you do not lose them to an update.
Always update themes and plugins first: Do not update WordPress before you update themes and plugins. The reverse should be the case.
Re-consider your plugin choices: Every WordPress update comes with enhancements and some of them add the functionality of some plugins. You need to consider WordPress enhancements and evaluate that in relation to any plugin functionality that had been added to WordPress core. You may just not need the plugin anymore.

How Does a Plugin Installation or Update Break Your Website

The fact is that plugins are not always perfect. It does not matter whether you got it from the WordPress official website or from a well trusted developer, there could be a problem because it could conflict with another plugin or with WordPress itself. The result is that you could lose your customizations; your website could behave strangely and sometimes could lead to "White Screen of Death".

What Next After a Site Breakdown

If you have suffered this problem before, you will understand how frustrating it can be to find an immediate solution. Never worry; there are a couple of steps you can take to fix the problem.

Restore an earlier backup. A backup is always the assurance you have when things get out of hand. If you have tried all fixes and nothing seem to work, simply as your web host to restore your backup or do it yourself if your hosting environment permits.
If you have access to the WordPress dashboard, follow these steps to fix your site:

If you updated your plugins one at a time, then you should know which plugin has caused the problem.
Simply deactivate it.
Check the website if things are working fine. If everything works fine, completely delete the plugin and report the problem to the plugin developer. You can always get another good replacement for the plugin if you choose to have the functionality on your website.

If you do not have access to the WordPress dashboard, follow these steps to correct the problem:

Access the file structure of your site by using either ftp (preferable) or your host’s file manager.
Locate the plugins folder. It should be located at wp-content/plugins and all of your plugins will have their own folder within that plugin folder.
If your updated was done one at a time, then it should be easy for you to locate the plugin that caused the problem. If you have updated just one plugin, the finding the culprit should be much easier.
Once you locate the problematic plugin, deactivate it by deleting the plugin’s folder.
Now, test the website to see if everything is working fine.
Contact the developer and report the problem and get a replacement from the WordPress repository.

What If This Fails to Work?

There is still a way out if you are unable to find a solution from the steps outlined above, there are still some things you could do:

The first thing you will need to do is to deactivate the WordPress theme you are using and switch to the default theme. WordPress will always work with no theme activated. If that does not fix your problem, then you are likely to have a corrupted WordPress and you will simply have to redo the update of your WordPress installation using FTP. That should address your problem.

Warning: If you have made changes to your images by way of overwriting default images, you will need to delete your images folder before overwriting your WordPress files in order not to lose the changes you have made to your images.

What is Then the Safe Way to Install WordPress

Begin with a backup:

Mae sure you have a safe and recent backup. A clean backup will be your last option should anything go wrong with your update.

The are backup plugins you will find useful available in the WordPress repository:

BackWPUp – Free plugin
Duplicator – The pro version of this plugin can be used for scheduling backups.
BackupBuddy – Paid plugin. Good for scheduling and migrations.
UpDraftPlus – Similar to BackWPUp and BackupBuddy. This plugin has been favoured by many WordPress users.
VaultPress – With this plugin, you can restore to the previous day with one-click. This plugin will automatically provide a backup for you within 30 days. No need saving in a different location.

Replace old and abandoned plugins. Any plugin that has not been updated for up to six months should further be investigated and any that has not been updated for up to 2 years should be replaced with a good alternative. Any plugin that is not being maintained poses a security risk to your website.
keep your plugins regularly updated. Patches and bug fixes and security fixes must be kept in mind to prevent problems.
Where you intend to update your plugins and WordPress core, ensure that you update plugins first. After updating, you may want to check for compatibility issues with your plugins. If a plugin goes along with a theme, you may consider updating the theme as well for the plugin to work properly

Did we miss anything; do let us know in the comment box. What other ideas do you have.

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Credit: https://www.todhost.com/blog/web-hosting-tips/94-how-a-plugin-installation-can-crash-your-wordpress-website