How to Stress Test a Website on WordPress

Speed is crucial to your site’s success. In order to keep your visitors happy, you’ll want to make sure your website performs well at all times and can handle large amounts of traffic. However, you might not know how to stress test your website to determine this.

Fortunately, the process is fairly simple. There are several tools you can use, and once you learn how to interpret the results, you can easily make the necessary changes to improve the performance of your WordPress site.

➡ In this post, we’ll take a closer look at stress testing and why it’s important. Then, we’ll show you how to stress test your website and resolve common performance issues. Let’s get started!

What is stress testing?

Your website is designed to handle a certain amount of traffic. This is normally determined by the capacity of your hosting plan.

📌 For instance, if you have a limited number of server resources, a sudden spike in traffic can take your site down. That’s why advanced hosting solutions such as virtual private server (VPS) and dedicated hosting are typically ideal for large websites with high traffic.

👉 However, your site’s performance is also affected by other factors, such as your theme and plugins. Heavy tools, unoptimized images, and unnecessary code can lead to slow loading times, especially during peak hours.

A stress test is designed to help you determine your site’s performance under different, strained conditions. Using this technique, you can simulate a high amount of traffic to your site to see if it can handle it.

Depending on the tool you use, you might be able to test your site for low, medium, and high traffic, then compare the results. For example, you can check how long your site takes to load when it has a particular number of users visiting it at the same time. Then, you can use your findings to optimize your site for better performance.

How to stress test your WordPress website

There are several tools you can use to stress test your website. In this tutorial, we’ll be using Loader.io:

The Loader.io homepage

This is a freemium tool that enables you to easily test your website for different amounts of traffic. The free plan lets you check one target host (your website) and two URLs per test. There’s also a maximum of 10,000 clients (or visitors) per test.

The free version may be enough for small websites. Although, if you have a busier website and want to simulate a high amount of traffic, you might want to opt for a premium plan. With this in mind, let’s look at how to stress test your website with Loader.io. 👇

Step 1: Sign up for Loader.io and verify your domain

First, you’ll need to sign up for a free Loader.io account. This is a very straightforward process. Once you verify your account, you can set up your target host (or domain):

Creating a new host in Loader.io to stress test website

👉 However, you’ll also need to verify that you own the domain that you’ll be testing. Verification is important to avoid abuse (as sending this much traffic to someone else’s website could be seen as a DDoS attack).

To start, click on + New Host and enter your domain on the following screen:

Adding a new target host in Loader.io to stress test website

You’ll then be asked to verify your domain. If you’re using the free plan, you can only verify via HTTP. To do this, click on the download link to save the file to your computer:

Verifying the domain in Loader.io to stress test website

Then, you’ll need to upload this saved file to your site’s root folder. This means you’ll need to connect to your website via a File Transfer Protocol (FTP) client such as FileZilla.

Once you’ve connected, locate the root folder. It’s usually called public_html. Then, upload the Loader.io file you’ve just downloaded to this core folder:

Adding the loader file to site's root folder in FileZilla.

When you’re ready, return to Loader.io and click on Verify. You should then see a message confirming that your domain has been verified:

Verification message in Loader.io

That’s it! You can now click on New Test to get started.

Step 2: Configure your test testings

Loader.io comes with various settings for your stress test. For example, you can select the type of test you want to run:

The test settings in Loader.io to stress test website

There are three test options to choose from:

  • Clients per test.For instance, you can see how your site performs when 600 users access it for one minute. In this scenario, clients will be distributed evenly throughout the test.
  • Clients per second. This will test your site for a specified number of client requests per second.
  • Maintain client load. With this option, your site will be stress tested for a constant load of users within a specified timeframe.

Note that you can run more than one test. In fact, it would be wise to do so. That way, you have a comprehensive view of how your site will perform under a variety of conditions.

For this tutorial, we’ll be using the Maintain client load option. This simulates a specified number of users accessing your site concurrently over a set amount of time, and remaining active during that period. This will enable you to see the average loading time for these users.

Once you’ve selected this test type, the next step is to specify the number of clients (or users) and the duration of the test. For example, you might want to test the performance of your site when it receives 500 visits in one minute.

If you click on Advanced Settings, you can set an error threshold, too:

Setting the error treshold in Loader.io

This means that any request that takes longer than your set threshold (e.g., 15 seconds) will return as a failed request.

If you scroll down, you’ll also find some settings for client requests:

Settings for Client Requests

You don’t need to make any adjustments here, unless you have some specific requirements. For a general stress test, the current settings will do. When you’re ready, click on Run test.

Step 3: Analyze your results

Once the test has been completed, you’ll get a detailed breakdown of the results. Let’s look at the most important metrics, starting with the graph:

The graph for the stress test

Here, we can see two sets of data. The green line represents the number of clients and the blue one represents the average response time. The graph shows that there were a total of 20 clients added over a 30-second period.

As the graph clearly demonstrates, the higher the number of users, the higher the average response time. However, there was a sharp decline when the 20th client was added. This indicates that the response time for this user was going to be higher than the error threshold that we set at 15 seconds. This resulted in a timeout.

If we look at the information in the Response Counts section, we’ll find that there are 19 successful responses and one fail:

The results for the stress test in Loader

As you can see, the average response time for this test was 7210ms, which is 7.21 seconds. This indicates a slow loading time when the site is being accessed by 20 users concurrently.

The fastest response time was 1.8 seconds, and the slowest was 15.2 seconds (our failed request). Considering these results, it is clear that the fastest loading time was recorded when the site had the minimum number of users.

Once you’ve analyzed your results, you can edit the test settings to add more clients. Then, you can re-run the test to see if your site can handle the extra load. You can continue to gradually add more clients until your site breaks. In this way, you can identify the maximum number of users your site can handle at once.

Resolving site performance issues

If your stress test results show that your site loads slowly during high traffic, don’t worry, there are plenty of ways to improve its performance. Let’s look at some effective strategies. 👇

  1. Set up a content delivery network (CDN)
  2. Use a caching tool
  3. Compress your images
  4. Remove heavy plugins

1. Set up a content delivery network (CDN)

A content delivery network (CDN) is a system of servers distributed across different locations. When you use a CDN, your users are served cached copies of your site from the server that’s closest to their location. This way, your content has a shorter distance to travel and therefore loads faster for the visitor.

Additionally, a CDN can minimize the load on your hosting server. This can further improve your loading times, which may in turn help boost your Core Web Vitals score.

2. Use a caching tool

Page caching is the process of storing static versions of your website and serving them to visitors. When you’re using caching, the browser won’t have to load heavy scripts when users access your site.

Caching can therefore improve your site’s speed and performance. You can use a tool such as WP Super Cache to serve static pages to your visitors:

3. Compress your images

Another contributing factor to poor performance is unoptimized files. If your site contains a lot of large files (such as images and videos), your pages will likely take longer to load. This also means that your site might run slower when accessed by a lot of people at the same time.

You can fix this problem by using an image optimization tool such as Optimole:

This tool compresses your images without compromising their quality. Also, it serves your images via a CDN, which can help further reduce loading times.

4. Remove heavy plugins

You might also consider removing heavy plugins from your site. These add bloat to your WordPress website by loading unused scripts and can therefore slow it down.

Alternatively, you could use a tool like Autoptimize to minify your code, including CSS, JavaScript, and HTML. This plugin can also inline critical CSS and lazy-load your images for a smoother User Experience (UX).

Start stress testing your website today

A stress test can help you determine your site’s performance during peak hours. You can use a testing tool such as Loader.io to simulate high amounts of traffic to your site within a specified timeframe and see how it fares under those conditions.

For instance, you can test your site’s response time when it receives 100 client requests in 30 seconds. You can then use the results to identify issues and improve your loading times. This might involve compressing your images, using a CDN or caching tool, and removing heavy plugins.

Do you still have any questions about how to stress test a website? Let us know in the comments section below!

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