This post from last week by Kirk McElhearn and this followup today by Michael Tsai reminded me that Safari 9 has a new feature in the Develop menu: Responsive Design Mode. Unfortunately, it’s not as smart as I’d hoped it would be. Or maybe I’m not.

The idea behind RDM is to let web designers see what a site looks like on smaller (Apple) screens without continually resizing windows or reloading pages on other devices. You can see how it looks by just clicking a button associated with the device of interest. And, unlike pinned sites, this feature is available on Safari 9 even if you’re still running Yosemite.

I’m not a web designer, but I am responsible for this site, and I do occasionally fiddle with its layout. I (finally!) made a mobile layout back in June, and it would have been much easier if I’d been able to see the results of my CSS changes immediately on my Mac as I made them.

But I soon found that RDM doesn’t really emulate smaller devices. Here’s what my site looks like on my iPhone 5s:

iPhone 5s view

And here’s what it looks like in Safari RDM:

Safari Responsive Design Mode

Not exactly a faithful representation. And it’s no better in landscape.

iPhone 5s landscape view

Safari RDM landscape

I assume this is at least partially because I don’t really know what I’m doing. I have two CSS files for the site: the original style.css that’s meant for wider screens and mobile.css that’s meant for narrower screens. The file used is controlled by these three lines in the <head>:

<link rel="stylesheet" type="text/css" media="all and (max-device-width:480px) and (orientation:portrait)" href="resources/mobile.css" />
<link rel="stylesheet" type="text/css" media="all and (max-device-width:480px) and (orientation:landscape)" href="resources/style.css" />
<link rel="stylesheet" type="text/css" media="all and (min-device-width:480px)" href="resources/style.css" />

So I’m really choosing the style file on the basis of the device’s width, not the view’s width. This is a simple solution, and it works, even though it isn’t fully responsive. If you’re reading this on a phone and rotate it, the layout will change; but if you’re reading this on a notebook or desktop computer and make the browser window narrow, the layout won’t change.

I don’t really want to mess with the site’s layout again, and I certainly wouldn’t do so just to get it to work in Safari’s RDM, but there are two things that’ll probably force me into it: iOS 9’s Slide Over and Split View on iPads. I’m pretty sure those views don’t change the device-width, and if I want the site to display its narrow layout when it’s in those modes, I’ll have to make it truly responsive.

Eventually. I’m not particularly responsive, either.