Mark has written down some thoughts on breakpoints in responsive designs. I share his concern that by settling on just a few breakpoints, there’s a danger of returning to the process of simply designing for some set canvases: here’s my “mobile” layout, here’s my “tablet” layout, here’s my “desktop” layout.
In my experience, not all breakpoints are created equal. Sure, there are the points at which the layout needs to change drastically in order for the content not to look like crap—those media queries can legitimately be called breakpoints. But then there are the media queries that are used to finesse page elements without making any major changes to the layout.
When I was working on Matter, for example, there was really only one major breakpoint, where the layout shifts from one column to two. That’s the kind of breakpoint that you can figure out pretty easily from the flow of your content; just resizing your browser window is usually enough to settle on the point that feels right. But there are lots of other media queries in the Matter stylesheet. Those are there to make smaller adjustments to margins, font sizes …the kind of changes that came about from testing on phones and tablets in the device lab.
It feels a bit odd to call them breakpoints, as though the layout would “break” without them. Those media queries are there to tweak the layout. They’re not breakpoints; they’re tweakpoints.