« Browser Choice vs Font Rendering
This post by Jeffrey Zeldman on font rendering in web browsers is a good introduction to the subject in a number of respects, but unfortunately repeats a pernicious myth: that web browsers on Windows all render text differently, and that this interacts with the OS rendering. There are a couple of caveats (see below), but for the most part, this a this is a system level setting. On any given Windows computer running XP or Vista or Windows 7, you will generally get >pixel-for-pixel identical glyph rendering in Internet Explorer, Firefox, Chrome, or Safari. (As also shown in Si Daniels’ presentation at ATypI 2009 in Mexico City).
Why is this? All of today’s major web browsers on Windows (IE, Firefox, Chrome, Safari) simply use the OS’s user-adjustable GDI text rendering settings, whatever those may be. Similarly, all today’s major web browsers on Mac OS simply use the system text rendering.
(Yes, there are a couple of caveats. Internet Explorer 7 actually ignores the OS setting in favor of its own prefs setting, which is to use the OSes ClearType rendering regardless. Safari for Windows has an optional setting to use Apple’s “Quartz” text rendering, even on Windows—this was the one-and-only rendering option in Safari 3 for Windows, but Windows users “freaked,” so Apple changed it for Safari 4 for Windows. Also, Firefox can use the kerning built into fonts, which affects spacing, though it doesn’t actually impact rendering of individual glyphs. Every major browser uses the same rendering as some version of OS rendering, however; none does something unrelated to Mac or Windows text rendering.)
So why does rendering vary so much? Windows XP, Vista and Windows 7 can be set to one of three settings for “font smoothing” (a.k.a. anti-aliasing). These settings affect all applications using the old-school GDI APIs for text rendering, which as of late 2009 means all the major web browsers. The font smoothing settings are:
- off (uncheck the box that says “use the following method to smooth the edges of screen fonts)
- Standard (grayscale)
- ClearType (optimization for color LCD screens)
Note that the standard vs ClearType distinction only affects fonts with TrueType outlines. Fonts in PostScript Type 1 or OpenType CFF formats get a less sophisticated type rendering/smoothing which, well, seems less than stellar these days.
“Standard” (grayscale anti-aliasing) is the default on Windows XP, although installing Internet Explorer 8 will change that setting to “ClearType” (even if one then proceeds to use a different web browser). Windows Vista and Windows 7 default to ClearType. So, most folks on Windows are seeing ClearType rendering, one way or another. However,
Besides GDI (all of today’s browsers), there is a completely different rendering mode used by applications which are programmed to use the “DirectWrite” text APIs (similar rendering also available to the largely-ignored WPF APIs). This uses ClearType, but a ClearType which is improved over the GDI version. For TrueType outlines, It offers moderate but noticeable improvements, such as options for improved spacing, and anti-aliasing in the Y direction. OpenType CFF fonts see a truly dramatic improvement, going from really mediocre rendering under GDI to rendering roughly equally well with TrueType under DirectWrite (or under its predecessor, WPF)! Minion Pro and Myriad Pro in OpenType CFF render pretty well down to 9 pixels per em (ppem), and just fabulously at 12 or more.
[Post updated 8 Jan 2010 to correct IE 7 having a built in pref for which OS rendering it uses. Thanks to commenters! - T]