Why Is Craigslist So Slow? Here Are The Reasons

Craigslist is by far the most popular classifieds website on the internet. According to SimilarWeb, the website receives over 200 million visits each month with 94% of the traffic coming from the United States.

A speed report from Lighthouse paints a rather grim picture and scores the Craigslist website 11.9 seconds on the speed index (SI), and 42% on Performance.

There are many reasons why the Craigslist website is so slow. This includes:

  • Bloated JavaScript files
  • Unused CSS files
  • Render Blocking Resources
  • Large DOM Size
  • Inefficient Scrolling Performance
  • Ineffective Caching Policy

Let’s look at each of these reasons and identify potential ways that Craigslist can make its website load faster.

But before we do that, a quick word about our website - we are a free email alert service that sends out notification any time your website is loading very slowly (often due to heavy traffic, or poor scripts). If you have a website, consider setting up an alert so that you can fix issues before they become major. 

Bloated JavaScript files

Craigslist uses a lot of JavaScript to run the website. However, loading them all from one source could slow up the performance of the website. Craigslist can avoid this by splitting the code into smaller files. This way, you only load files that are necessary.

The Craigslist website can be as much as 1.2 seconds faster by adopting this technique.

Unused CSS files

Craigslist uses CSS files to load the styling elements for the website. However, this file contains a lot of unused scripts that can be slowing down page loading by as much as 0.3 seconds. Code splitting may help avoid this issue.

Render-blocking resources

There are scripts on the Craigslist website that need to run first before they let the rest of the code be executed. The render-blocking resources issue can shave off around 0.83 seconds from the loading time for the Craigslist website.

How do you avoid this? If the script is not critical, avoid having it in the <head> tag of your HTML code. But if you do need to have it there for some reason, make sure to include the defer or async attribute so that they do not block the loading of other resources.

Large DOM size

The Craigslist website takes close to 2.4 seconds to evaluate all the scripts, parse them, compile, and render them. This can be minimized by minimizing the main-thread work.

They may also look at reducing the number of nodes in the DOM. In simpler terms, you need to make sure that the main HTML code is smaller and has fewer nodes. I have explained this in greater detail in this article about DOMContentLoaded.

Inefficient Scrolling Performance

When you load Craigslist, you may notice a scroll jank – that is, the page stops responding to clicks and scrolls for a bit before catching up. This happens because the Craigslist website contains a bunch of JavaScript files with ‘active listeners’ that prevent the browser from scrolling until they are completely loaded. This can be easily avoided by the use of passive listeners – just a small tweak to code that can make your page load more seamlessly.

Ineffective Caching Policy

A website like Craigslist is made of several components, including a lot of images, and other media files. Caching, or storing these components in your local computer, enables your browser to load the website much faster when you come back a second or third time.

With Craigslist, however, the cache for most media files clear is deleted every 30 days. This means that the website is loaded completely from scratch any time you visit after 30 minutes. Enabling a longer cache period could make loading pages faster and more user-friendly.

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