2019-01-04 07:00:00 -0300 - olaolu

We’ve learnt already in the first part of this web performance series why performance is important, and should be included at every stage of product design, what benefits it holds for businesses and products, and the negatives of poor performance. Now, let’s talk about the problems of web performance; what makes sites slow. So, let’s get started!

What makes sites slow

No doubt, there’s a whole lot of reasons why websites are slow. Some of which are peculiar to that site. I like to look at these factors from two perspectives:

Really, the user and the developer are the two main parties involved in this discussion; all other factors that impact web performance like the network from which the site is accessed, the hardware specs of the device, and the software fall under the user factor. Same way, developers are responsible for what ever impacts performance on the tech part of it. So, basically, these two guys are the players in this game.

That being said, in this article, we’ll look at things less from user perspective, and focus on the development side because most of the problems come from there, and to move forward, developers have to build with the users in mind and the various real-life situations they could be caught up in because we definitely can’t control them; we can’t move all our users to a luxury place with super-fast internet connection and great devices — that’s unrealistic. So, let’s jump right in to what makes sites on the internet slow today.

Apart from network, hardware, and software limitations which are user factors, let’s actually talk about the technical causes of poor performance on the front end.

1. Third-party Resources and Scripts

It’s a common and normal practice to have third-party resources and scripts on our sites because we most of the time consume third-party content and services whether it’s analytics, ads, social media plugin-ins, framework/library resources — we use them.

However, so many times, the authors of these third-party resources just tell us to plug in their resources to our sites: resources that might depend on other resources all the way down or may be poorly written, and then they serve us. The fact however remains that most of these assets are the leading cause of performance problems on the web because of course, we didn’t build them, we don’t know how they were built, we do not own them, all we want is their services, so we can’t determine the quality of these services.

It’s sad news that third-party resources today have control on a lot of sites today, and then as developers, most of the time we’re just lazy to take it back. I’ve personally seen several situations where sites include a whole mighty resource, and then end up using a very minimal portion of it, say 5% or something.

It’s usually not a great idea to do that, there’s a lot of stuff we can do on our own without relying on these resources. You don’t have to include a 300kb UILibraryX, meanwhile you’re using one of its component that’s about 5kb.

2. Super heavy Assets and Resources

We all have that one big file on our sites, that one big JavaScript asset or 1MB image from Unsplash. Really, it’s quite difficult to manage these file sizes when everyone is in a rush, bent on results, and then we all just forget performance, something that our users are very well aware of. Users know when your site is slow, they also know most times what sites consume their data a lot. Generally, JavaScript occupies the top position on the list of front end resources that impact performance negatively, followed by images.

As developers, we write code that looks good to us, we do things that make us feel satisfied, but we just forget that priority in this context should be given to the user — what the user needs, what a great experience is like to them. The user doesn’t know how fancy your code is, they don’t really care how fancy your images are. They just want to be able to use your site and have great experiences. If your site is not accessible quickly, you don’t even get the chance to show your “fancy image”. We’ll talk on how to resolve these problems in next article on optimizing performance.

3. Excessive HTTP Requests

Get! Post! Front end developers, we love to do that a lot: consuming APIs and all — it’s fun actually, being able to tell a web server what to do, that’s power to an extent, right? Yeah, yeah, it’s awesome!

But at the same time, it’s not — winks. Sending requests back and forth can be too much to handle. Imagine a superior at your office; one day you’re going to get a snack and then, he calls “hey, on your way, get me some venti iced skinny hazelnut macchiato, sugar-free syrup, extra shot, light ice, no whip coffee from starbucks”. Extremely weird and confusing, right?

Similar can happen with your server when making requests. If you observe from that order, the most important thing to you is actually getting your snack either to keep your mouth busy or satisfy you, just the way your users want to use your product — they want to satisfy themselves. Too bad your superior took that power away from you LOL. You know how tough it can be to say no to that, same way the server can’t say no to your multiple requests. It just must handle it no matter how complicated it is.

Your user might not need all the junks and stuff you’re fetching for them on the initial load, they need what matters, and you’re in place to answer those questions. Answer to the things you’d want to have on your screen quickly if you were the user.

4. Poor Code Quality

Yes, bad code. Every one likes to jump on a computer and start writing code endlessly, however, this excitement should leave us with the questions: “Am I doing it the right way?”, “Can this be done better?”, “What are the implications of doing it this way?”.

A lot from the code quality can affect the performance of your site or product as an entity. Whether you’re writing a component that should take 10 lines of code in 50 lines, or you there’s so much dead code, or you’re just writing the code or using a tool in a way that it’s much slower to function; they all impact performance. For example, having excessive whitespace and dead code blow up file sizes and in turn, affects performance.

In fact, all the points listed previously in one way or the other fall under the quality of code you’re delivering and how experienced or competent a developer is. Your JavaScript, CSS, HTML and other applications on the back end contribute to performance directly or indirectly.

There are some industry standards and practices that should be followed while building your sites. Don’t write code that “just works™”. You should consider if you’re actually solving that problem in the most efficient way.


Now that you have a clearer view on why performance matters and the several factors that influence performance, including a few instances of not-so-good practices. In the next article, we’ll finally talk about the strategies and patterns to tackle these problems.

In summary, how we build what we build matters, because that’s always a huge part of the product no matter what it is. That’s what we serve users, and we should care more about what matters to the user, and not how quickly we can achieve something that might not be the best experience for users.

Further Reading and Resources…

Love this article? Feel free to share with your followers, team, or employer. Also, I tweet cool stuff on Twitter @mrolaolu, you should follow me!

Thanks for reading!