Why Do We Separate HTML and CSS

When you start learning web development, you might wonder why we separate HTML and CSS. It is actually one of the best practices we follow when it comes to coding. But do you know why separating HTML and CSS is a good idea?

Separating HTML and CSS means you can change how a web page looks without having to touch the code that describes its structure. You can easily change your website by swapping one style sheet for another without worrying about breaking anything else in your site’s code.

Read on to find out why some web developers prefer keeping HTML and CSS separate and others prefer to inline their styles.

It Is a Good Idea To Use CSS With HTML

A web page needs HTML and CSS to look good on your screen.

HTML or Hypertext Markup Language gives the page structure but doesn’t add any style. So, it will show all the menus, headers, text, links, etc., but only plain text with no colors, alignment, or placement of items.

CSS, which stands for “Cascading Style Sheets,” is the code that tells your items where to go, adds color, styles your text (underlining, bolding, and italicizing), colors your background, and does a lot more.

css separated from html
It is standard practice to have the HTML file (index.html on the left side of the image) and CSS (style.css below it) separated for better file organization and performance. On the screenshot you can also see an example of inline CSS (p tag on line 13)

Keeping HTML and CSS Separate Improves Efficiency

Even though it’s not required, it’s typically preferable to have HTML and CSS in their own files for efficiency and architectural reasons.

If you have shared styles used on several pages, they can be delivered via a single CSS file with cache headers set (expires headers). When you navigate to the next page, the user no longer needs to download the CSS, resulting in a faster experience and less data consumption. When stylesheets are served inline, they must be downloaded with each page request, which can be inefficient for multi-page websites.

Another way to improve efficiency is by removing HTML comments. See how HTML comments affect performance in my guide on the topic. You’ll learn how to balance performance and documentation.

The following are some other considerations that suggest keeping CSS and HTML apart:

Content Before Design

It’s easier to maintain a consistent look and feel across multiple pages if you have all of your styling information in one place. You only need to adjust one file if you need to change your site’s colors, fonts, or layout.

By keeping your HTML and CSS files separate, you can also get started on your content even before you’ve settled on how it will look; you’ll be able to style the pages with relative ease after you’ve decided on the look. There may be minor adjustments to the HTML, such as adding tags or class and id properties.

If you decide you don’t like the way your pages look down the road, you can simply modify a single CSS file to make the entire site seem different.

Useful info: Do you know there are more than a hundred HTML tags? In years of my career, I have come nowhere near using the majority of them. But there are some standard ones that I use daily.

HTML and CSS Are Semantically Independent

HTML and CSS are used to structure a website, but they do different things. HTML is all about content–it tells the browser what each page part is, while CSS defines how that content looks. 

Separating them is the correct semantic action because it allows each language to do what it does best. Your code will be easier to read and understand, and other developers can follow along with what you’ve done more efficiently.

You May Have Different CSS and HTML Developers

This is a common scenario for bigger projects or if you’re just starting with front-end development. If that’s the case, it’s easier for the developers to work on their own files than in one giant file together. It also keeps things organized when it comes time to check code changes!

You Don’t Always Need to Separate HTML From CSS

You don’t always need to separate HTML from CSS. Sometimes, it’s better to inline your CSS in your HTML.

Here are some reasons why you might want to do that:

  • Performance. If you have a single page that needs to load quickly, it can be helpful to inline your CSS so that the browser doesn’t have to go out and fetch it from another file.
  • Overriding stylesheets. If you want to override the default stylesheet for some reason (maybe you want to change the color of all buttons on the site), this is easier if you don’t have two separate files for each area of your site.
  • Quick demos. Sometimes we just want things done quickly and don’t want to spend time separating files or tweaking settings in our code editor, so we’ll just use inline CSS until we get around to organizing things properly later on down the road!
Inline css example
Example of inline CSS.

HTML and CSS Alone Won’t Make an Incredible Website

If you’re looking to build a website, you’re probably starting with HTML and CSS–which is great! These two languages are incredibly powerful and can do some amazing things. But there are also some limitations.

One thing that is really important to know about HTML is that it’s not dynamic. It doesn’t have any way to change what content is displayed on the page based on user input or other factors like time or location. That means that when you build your site using just HTML and CSS, there are only so many ways you can make it interesting for users.

JavaScript is what makes your site dynamic. It lets you add interactivity and responsiveness to your pages so they can do more than just look pretty. And if you want to get really fancy? You can combine JavaScript with HTML and CSS by using a library like jQuery, which gives even more options for creating exciting experiences for users who visit your site.

Interested in learning more about HTML? Find out if you can open an HTML file without internet access. You’ll learn a few tricks along the way, too.


Isn’t it nice to have independent control over HTML and CSS, with the opportunity to customize each without affecting the other? In theory, you can have one person responsible for HTML and another dedicated to CSS. Or you can keep all the coding in one place but separate the elements so they are easy to manage. This makes collaboration and customization easier.

On the other hand, separating HTML and CSS isn’t always necessary; fewer files also translate into faster load times, so if all you do is a simple task, using one document should suffice just fine.