Type should be part of the body of the computer, and not just the clothing which it wears. — Matthew Carter

The final release of Safari 11.0 marks the moment when front-end developers should take note of the OpenType 1.8 Variable Fonts spec. As macOS High Sierra shows up beginning today to Apple laptops and desktops, and as iOS 11 continues its proliferation to the world’s iPhones and iPads, we will soon see Safari 11.0 represent a majority of web browser traffic — and with that, full support for variable fonts! (Though non-Safari browsers have not yet enabled support in stable-channel releases, you can test it in Chrome Canary, or after making adjustments in about:config for Firefox Nightly and Developer Editions.)

The variable fonts spec actually isn’t a newly-found idea. It originated in Apple’s TrueType GX Variations technology, released during the Font Wars, an epic period of controversy two decades ago that pitted Apple, who pushed for an OS-level font format, against Adobe et.al., who fought to hold the ground gained by their application-level “page description language” tools such as PostScript and their Multiple Masters font spec.

Tom Rickner describes the things in this post:

Adobe did not sit idly by during this period. Just 2 months before Apple was able to ship a TrueType enabled System 7, Adobe announced Multiple Masters. With this format, a designer would draw the extreme combinations in each “axis of variation”… and the user could then interpolate intermediate designs within this design space…

… which is a logical approach, but for one key exception:

As we looked at Multiple Masters, the first thing we all realized was that Adobe was not drawing or storing data for the primary, or the default font in the family. Since it interpolated from extreme values, the designer had to draw the shapes that define the outer edges of the design space, as we’ve previously seen. Mike [Reed] thought a more useful approach would involve starting with the primary weight, or another existing weight or style, since these fonts already exist, and in our case they were already instructed in TrueType….

I don’t understand why Adobe opted to interpolate the default font. Aren’t extremes, by definition, an exception to the rule?


Then Mike considered the Delta instruction. One of the unique attributes of the TrueType Delta instruction, is that it works with arbitrary directionality. So the instruction doesn’t only work in the X direction or the Y direction, but instead can be applied parallel or perpendicular to any two points in a glyph’s outline, or on computed angles for that matter.

Brilliant solution. The notion that a font’s default configuration should be the standard upon which its variations are built! #uncommonsense

So, fast-forward to today. Apple devices now have support for Variable Fonts, in anticipation of font foundries producing more type definitions that comply with the OpenType 1.8 spec, and as web developers incorporate those new definitions in their approach to page typography and responsive design.

I’ll definitely be looking for Variable Fonts support in any typeface I choose from now on. It’s enough of a reason to prefer a font over the others, as I can be more certain of the browser’s ability to render the most legible text as intended by the glyph designer who I have no doubt knows more about visual subtlety than I do.