[css] Single huge .css file vs. multiple smaller specific .css files?

Is there any advantage to having a single monster .css file that contains style elements that will be used on almost every page?

I'm thinking that for ease of management, I'd like to pull out different types of CSS into a few files, and include every file in my main <link /> is that bad?

I'm thinking this is better

1. positions.css
2. buttons.css
3. tables.css
4. copy.css

vs.

1. site.css

Have you seen any gotchas with doing it one way vs. the other?

There is a tipping point at which it's beneficial to have more than one css file.

A site with 1M+ pages, which the average user is likely to only ever see say 5 of, might have a stylesheet of immense proportions, so trying to save the overhead of a single additional request per page load by having a massive initial download is false economy.

Stretch the argument to the extreme limit - it's like suggesting that there should be one large stylesheet maintained for the entire web. Clearly nonsensical.

The tipping point will be different for each site though so there's no hard and fast rule. It will depend upon the quantity of unique css per page, the number of pages, and the number of pages the average user is likely to routinely encounter while using the site.

You want both worlds.

You want multiple CSS files because your sanity is a terrible thing to waste.

At the same time, it's better to have a single, large file.

The solution is to have some mechanism that combines the multiple files in to a single file.

One example is something like

<link rel="stylesheet" type="text/css" href="allcss.php?files=positions.css,buttons.css,copy.css" />

Then, the allcss.php script handles concatenating the files and delivering them.

Ideally, the script would check the mod dates on all the files, creates a new composite if any of them changes, then returns that composite, and then checks against the If-Modified HTTP headers so as to not send redundant CSS.

This gives you the best of both worlds. Works great for JS as well.

I'm using Jammit to deal with my css files and use many different files for readability. Jammit doest all the dirty work of combining and compressing the files before deployment in production. This way, I've got many files in development but only one file in production.

Maybe take a look at compass, which is an open source CSS authoring framework. It's based on Sass so it supports cool things like variables, nesting, mixins and imports. Especially imports are useful if you want to keep seperate smaller CSS files but have them combined into 1 automatically (avoiding multiple slow HTTP calls). Compass adds to this a big set of pre-defined mixins that are easy for handling cross-browser stuff. It's written in Ruby but it can easily be used with any system....

I typically have a handful of CSS files:

• a "global" css file for resets and global styles
• "module" specific css files for pages that are logically grouped (maybe every page in a checkout wizard or something)
• "page" specific css files for overrides on the page (or, put this in a block on the individual page)

I am not really too concerned with multiple page requests for CSS files. Most people have decent bandwidth and I'm sure there are other optimizations that would have a far greater impact than combining all styles into one monolitic CSS file. The trade-off is between speed and maintainability, and I always lean towards maintainability. The YUI comperssor sounds pretty cool though, I might have to check that out.

Monolithic stylesheets do offer a lot of benefits (which are described in the other answers), however depending on the overall size of the stylesheet document you could run into problems in IE. IE has a limitation with how many selectors it will read from a single file. The limit is 4096 selectors. If you're monolithic stylesheet will have more than this you will want to split it. This limitation only rears it's ugly head in IE.

This is for all versions of IE.

See Ross Bruniges Blog and MSDN AddRule page.

You can just use one css file for performance and then comment out sections like this:

/******** Header ************/
//some css here

/******* End Header *********/


/******** Footer ************/
//some css here

/******* End Footer *********/

etc

SASS and LESS make this all really a moot point. The developer can set up effective component files and on compile combine them all. In SASS you can toggle off the Compressed Mode while in development for easier reading, and toggle it back on for production.

http://sass-lang.com http://lesscss.org

In the end a single minified CSS file is what you want regardless of the technique you use. Less CSS, Less HTTP requests, Less Demand on the server.

Historically, one of the main advantages x in having a single CSS file is the speed benefit when using HTTP1.1.

However, as of March 2018 over 80% of browsers now support HTTP2 which allows the browser to download multiple resources simultaneously as well as being able to push resources pre-emptively. Having a single CSS file for all pages means a larger than necessary file size. With proper design, I don't see any advantage in doing this other than its easier to code.

The ideal design for HTTP2 for best performance would be:

• Have a core CSS file which contains common styles used across all pages.
• Have page specific CSS in a separate file
• Use HTTP2 push CSS to minimise wait time (a cookie can be used to prevent repeated pushes)
• Optionally separate above the fold CSS and push this first and load the remaining CSS later (useful for low-bandwidth mobile devices)
• You could also load remaining CSS for the site or specific pages after the page has loaded if you want to speed up future page loads.

A bundled stylesheet may save page load performance but the more styles there are the slower the browser renders animations on the page you are on. This is caused by the huge amount of unused styles that may not be on the page you are on but the browser still has to calculate.

See: https://benfrain.com/css-performance-revisited-selectors-bloat-expensive-styles/

Bundled stylesheets advantages: - page load performance

Bundled stylesheets disadvantages: - slower behaviour, which can cause choppyness during scrolling, interactivity, animation,

Conclusion: To solve both problems, for production the ideal solution is to bundle all the css into one file to save on http requests, but use javascript to extract from that file, the css for the page you are on and update the head with it.

To know which shared components are needed per page, and to reduce complexity, it would be nice to have declared all the components this particular page uses - for example:

<style href="global.css" rel="stylesheet"/>
<body data-shared-css-components="x,y,z">

I prefer multiple CSS files during development. Management and debugging is much easier that way. However, I suggest that come deployment time you instead use a CSS minify tool like YUI Compressor which will merge your CSS files into one monolithic file.

The advantage to a single CSS file is transfer efficiency. Each HTTP request means a HTTP header response for each file requested, and that takes bandwidth.

I serve my CSS as a PHP file with the "text/css" mime type in the HTTP header. This way I can have multiple CSS files on the server side and use PHP includes to push them into a single file when requested by the user. Every modern browser receives the .php file with the CSS code and processes it as a .css file.

Having only one CSS file is better for the loading-time of your pages, as it means less HTTP requests.

Having several little CSS files means development is easier (at least, I think so : having one CSS file per module of your application makes things easier).

So, there are good reasons in both cases...

A solution that would allow you to get the best of both ideas would be :

• To develop using several small CSS files
  • i.e. easier to develop
• To have a build process for your application, that "combines" those files into one
  • That build process could also minify that big file, btw
  • It obviously means that your application must have some configuration stuff that allows it to swith from "multi-files mode" to "mono-file mode".
• And to use, in production, only the big file
  • i.e. faster loading pages

There are also some software that do that combining of CSS files at run-time, and not at build-time ; but doing it at run-time means eating a bit more CPU (and obvisouly requires some caching mecanism, to not re-generate the big file too often)

I prefer multiple CSS files. That way it is easier to swap "skins" in and out as you desire. The problem with one monolithic file is that it can get out of control and hard to manage. What if you want blue backgrounds but don't want the buttons to change? Just alter your backgrounds file. Etc.

This is a hard one to answer. Both options have their pros and cons in my opinion.

I personally don't love reading through a single HUGE CSS file, and maintaining it is very difficult. On the other hand, splitting it out causes extra http requests which could potentially slow things down.

My opinion would be one of two things.

1) If you know that your CSS will NEVER change once you've built it, I'd build multiple CSS files in the development stage (for readability), and then manually combine them before going live (to reduce http requests)

2) If you know that you're going to change your CSS once in a while, and need to keep it readable, I would build separate files and use code (providing you're using some sort of programming language) to combine them at runtime build time (runtime minification/combination is a resource pig).

With either option I would highly recommend caching on the client side in order to further reduce http requests.

EDIT:
I found this blog that shows how to combine CSS at runtime using nothing but code. Worth taking a look at (though I haven't tested it myself yet).

EDIT 2:
I've settled on using separate files in my design time, and a build process to minify and combine. This way I can have separate (manageable) css while I develop and a proper monolithic minified file at runtime. And I still have my static files and less system overhead because I'm not doing compression/minification at runtime.

note: for you shoppers out there, I highly suggest using bundler as part of your build process. Whether you're building from within your IDE, or from a build script, bundler can be executed on Windows via the included exe or can be run on any machine that is already running node.js.

here is the best way:

1. create a general css file with all shared code
2. insert all specific page css code into the same page, on the tag or using the attribute style="" for each page

on this way you have only one css with all shared code and an html page. by the way (and i know that this is not the right topic) you can also encode your images in base64 (but you can also do it with your js and css files). in this way you reduce even more http requests to 1.

I've created a systematic approach to CSS development. This way I can utilize a standard that never changes. First I started with the 960 grid system. Then I created single lines of css for basic layouts, margins, padding, fonts and sizes. I then string them together as needed. This allows me to keep a consistent layout across all of my projects and utilize the same css files over and over. Because they are not specific. Here's an example: ----div class="c12 bg0 m10 p5 white fl"/div--- This means that the container is 12 columns across, utilizes bg0 has margins of 10px padding of 5 the text is white and it floats left. I could easily change this by removing or adding a new - What I call a "light" style- Instead of creating a single class with all these attributes; I simply combine the single styles as I code the page. This allows me to create any combination of styles and does not limit my creativity or cause me to create a massive number of styles that are similar. Your style sheets become a lot more manageable, minimized and allow you to re-use it over and over. This method I have found to be fantastic for rapid design. I also no longer design first in PSD but in the browser which also saves time. In addition because I have also created a naming system for my backgrounds and page design attributes I simply change out my image file when creating a new project.(bg0 = body background according to my naming system) That means that if I previously had a white background with one project simply changing it to black simply means that on the next project bg0 will be a black background or another image..... I have not found anything wrong with this method yet and it seems to work very well.