`100% - 4rem` is for mobile. `70ch` is for desktop. The tiny column is intentional. It offers a better default reading experience than a widescreen monitor full of text.

It's an implementation of an old recommendation to never have more than 80 characters per line, ostensibly to limit horizontal eye movement but mostly stemming from legacy 80-character terminals and punch cards.

The value of that recommendation is rather dubious considering today's high-resolution displays that allow for smaller font sizes. 80 readable characters at 768p are not the same as 80 readable characters at 4K.

The 50-70 CPL is, in general, just well suited to reading. This has been researched, and by quickly searching I can find the following (beautifully layed out) paper: https://journals.uc.edu/index.php/vl/article/view/5765

To my surprise the paper actually concludes that fast readers prefer shorter line length.

Edit: Usually books and newspapers are also more or less in compliance with this convention and those where around since before computers where a thing.

As someone who uses screen zoom tools constantly, I vote in favour of the 80ch column width recommendation. If you want to support extra wide monitors, consider using multiple columns, rather than a single, wider one.

Multiple columns don't really work with websites, as web content almost always going to be vertically scrollable.

Columns work great for things like a navigation sidebar or an image grid, but it just doesn't play nice with long-form blog content.

Fair, but neither do long line lengths.

It actually goes back to mechanical typewriters, which were limited to 70 to 90 characters per line. Commonly used punch cards also had 80 columns. Both were the inspiration for the 80 characters in computer terminals.

Weeel, actually! ... It dates back to the early days of the printing press, and has been a general convention since then.

Rules can be broken, but not without consequence.

I hate this. Give us a small amount of padding and text wrap. Let users with large screens resize their browsers to whatever width they want. This isn't 1985, we don't have terminals with only 80 characters per line.

> Let users with large screens resize their browsers to whatever width they want.

Do people actually do this? I have like 10 tabs in a maximized browser window. Am I supposed to keep unmaximizing it and fidgeting with the width? Or am I supposed to just rip the tab out and have to deal with multiple browser windows?

You run a large, high resolution screen with your browser maximized?

I have a 4k screen. Most of the time I keep my browsers half width. For most sites it seems to be the best use of screen real estate. Even at half width that site's CSS restricts the width of the content too much, leaving a lot of wasted padding on either side.

> You run a large, high resolution screen with your browser maximized?

Probably like 98% of the time, yes.

It's not an ultrawide, just a 27" 16:9 screen.

I find small windows to perform poorly on anything that's not just a simple document (gmail, hacker news, etc) because those require some horizontal space.