4 Common Website Speed Bottlenecks You Need To Know

Published on March 25, 2025
Last Updated on May 7, 2025

Written by

Morgan Frank - Specialist in Page Speed

So, you know why page speed is important, and you understand the basic steps the browser takes to load a page (the Critical Rendering Path). Now it’s time to play detective and identify the common culprits that slow down websites. Think of these as the “usual suspects” in the case of the sluggish website.

These bottlenecks can occur at various stages, from the server to the browser. We’ll break them down into manageable categories.

Key Takeaways From The Survey

Here’s what we’ll explore:

  • Website speed bottlenecks can occur on the server, in the browser, or on the network.
  • Common server-side bottlenecks include slow hosting, high TTFB, unoptimized databases, and lack of caching.
  • Common front-end bottlenecks include unoptimized images, render-blocking resources, too many HTTP requests, unminified code, and not leveraging browser caching.
  • Network bottlenecks include slow user connections and not using a CDN.
  • Third-party scripts can significantly impact the performance.
website-bottlenecks-1

Server-Side Bottlenecks

These problems originate on the server that hosts your website.

  • Slow Hosting:

This is like having a slow delivery truck for your website’s files. If your hosting provider is underpowered or overloaded, it will take longer to respond to requests, delaying everything else. Shared hosting, where you share resources with many other websites, is often the slowest option.

  • Solution: Consider upgrading to a better hosting plan VPS, dedicated server, or cloud hosting) or switching to a more reputable provider.
  • Slow Server Response Time TTFB Time to First Byte):

This is the time it takes for the server to start sending the first byte of data after receiving a request. It’s like the time it takes for a chef to start cooking after you place your order. High TTFB indicates server-side problems.

  • Solution: Optimize your server configuration, database queries, and application code. Consider using server-side caching.
  • Unoptimized Databases:

If your website relies on a database (most websites do), slow database queries can be a major bottleneck. It’s like having a disorganized library where it takes forever to find the book you need.

  • Solution: Optimize your database queries, ensure proper indexing, and consider using a database caching layer.
  • Lack of Server-Side Caching:

Caching stores frequently accessed data so it can be served quickly without re-processing. Without caching, the server has to do the same work repeatedly, slowing things down. It’s like having to cook the same meal from scratch every time someone orders it.

  • Solution: Implement server-side caching (e.g., using tools like Varnish, Redis, or Memcached).
Server-Side-Bottlenecks

Front-End Bottlenecks (Browser-Side)

These problems occur in the user’s browser after the server has sent the files.

  • Unoptimized Images:

Large image files are one of the most common causes of slow page speed. It’s like trying to send a huge package through a narrow pipe.

  • Solution: Compress images (without sacrificing too much quality), use appropriate image formats ebP, AVIF are generally best), and use responsive images (serve different image sizes for different screen sizes).
  • Render-Blocking Resources CSS and JavaScript):

As we learned in the Critical Rendering Path explanation, the browser needs to download and process CSS and (often) JavaScript before it can display anything. These are “render-blocking” resources.

  • Solution:
  • CSS: Minimize CSS files, inline critical CSS (the CSS needed for above the-fold content), and defer non-critical CSS.
  • JavaScript: Minimize JavaScript files, defer JavaScript loading (using the defer attribute), load JavaScript asynchronously (using the async attribute) where possible, and use code splitting to load only the necessary JavaScript for each page.
  • Too Many HTTP Requests:

Every file your website needs HTML, CSS, JavaScript, images, fonts, etc.) requires a separate HTTP request. Too many requests can slow things down, especially on slower connections. It’s like having to make multiple trips to the grocery store instead of getting everything at once.

  • Solution: Combine CSS and JavaScript files (where appropriate), use CSS sprites for small images, and reduce the number of third-party scripts.
  • Unminified HTML, CSS, and JavaScript:

Minification removes unnecessary characters (like whitespace and comments) from code, reducing file size without affecting functionality. It’s like taking the air out of a package to make it smaller.

  • Solution: Use minification tools or plugins to automatically minify your code.
  • Not Leveraging Browser Caching:

Browser caching allows the browser to store copies of website files locally, so it doesn’t have to download them again on subsequent visits. Without caching, the browser has to download everything every time, which is much slower.

  • Solution: Set appropriate caching headers (e.g., Cache-Control, Expires) to tell the browser how long to store files.
Front End Bottlenecks Browser Side

Network Bottlenecks

These problems relate to the connection between the server and the user’s browser.

  • Slow Network Connection:

This is often outside of your control, but it’s important to remember that your users may have slow or unreliable internet connections, especially on mobile.

  • Solution: Optimize your website for speed as much as possible, so it performs well even on slower connections. Use a CDN.
  • No Content Delivery Network CDN:

A CDN stores copies of your website’s files on servers around the world. When a user visits your site, the CDN serves the files from the server closest to them, reducing latency and improving speed. It’s like having multiple warehouses around the world instead of just one.

  • Solution: Use a CDN to distribute your content globally.
Network Bottlenecks

Third-Party Scripts

  • Too much third party scripts:

Third-party scripts (like analytics trackers, social media widgets, and advertising scripts) can significantly slow down your website, especially if they’re not optimized.

  • Solution: Audit your third-party script, lazy load where possible, and Self-host if you can.

Conclusion

Identifying these “usual suspects” is the first step to fixing them. By systematically addressing these common bottlenecks, you can dramatically improve your website’s page speed, leading to a better user experience, improved SEO, and increased conversions. The next step is to learn how to measure your website’s performance and pinpoint the specific issues affecting your site. We’ll cover that in the next sections!

Shakeeb Sadikeen

The expert that experts learn from

About Author

Determined to change that, he built RapidLoad — a smart, AI-driven tool that empowers site owners to dramatically improve speed scores, enhance user experience, and meet Google’s Core Web Vitals without needing to touch a single line of code.
Check out the about page
Connect with Shakeeb Sadikeen

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