A Simple CSS Trick to Deal with Horizontal Scrollbars in Code Blocks

Yihui Xie 2023-08-28

The reading experience with horizontal scrollbars is often very bad. For most reading devices, it’s easy and natural to scroll vertically, but not so horizontally. It’s inconvenient and even annoying to have to scroll horizontally back and forth to read multiple lines of content one by one.

I have thought about this problem several times before, especially when I want style code blocks on HTML pages, but I didn’t come up with a satisfactory solution. Earlier this year I thought about it again, and decided to do the following:

  1. Hard-wrap the content inside code blocks:

    pre, pre:hover {
  white-space: pre-wrap;
  word-break: break-all;
}
pre code {
  display: block;
  overflow-x: auto;
}

  2. Cancel the hard-wrapping on larger screens:

    @media only screen and (min-width: 992px) {
  pre { white-space: pre; }
}

    That is, on larger screens, you will still see the horizontal scrollbars by default when certain lines are too wide, but if you move your mouse over the content, it will be hard-wrapped (due to pre:hover’s CSS above). On smaller screens, the content is always hard-wrapped, which means there will never be horizontal scrollbars.

To be honest, both horizontal scrollbars and hard-wrapped lines of code look ugly in my eyes. When I weigh the trouble in reading against the appearance, I decided to always wrap the lines on small devices because usually you don’t have a mouse there, and wrap the lines on large devices only when necessary, which saves vertical space by default, but readers can easily hover to view the full content without scrolling horizontally. When you move your cursor over a code block, it may be a good indicator that you are interested in reading it, and you may be (hopefully positively) surprised that the code block is automatically expanded for you so you can keep reading the full code.

Below is a simple demo. You can try to view it on a small device (e.g., your phone), and also on a large device (e.g., your computer). For the latter case, hover over the code block to see the horizontal scrollbar disappear.

code {
  font-family: 'DejaVu Sans Mono', 'Droid Sans Mono', 'Lucida Console', Consolas, Courier, 'Courier New', Monaco, monospace;
}
.draft {
  background: repeating-linear-gradient(135deg, white, white 30px, #ddd 32px, #ddd 32px);
}

I came up with this idea when designing the CSS for a new HTML slide format early this year. The code blocks are not wrapped by default, which can save me vertical space on slides (space on slides is often limited). When I really need to present the code to the audience, I can move my cursor over it.

I hope you will find this CSS trick useful, and I’m all ears to other ideas to solve this problem.