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IE9 and TTF and 'embedding bits'

27 March 2011

There has been some confusion around the fact that the new Internet Explorer 9 ignores TTF webfonts whose 'embedding bits' are not set to 'installable'.[1] Does this mean that type foundries need to set their webfonts' 'embedding bits' to 'installable' or that those who license webfonts for hosting them on their own webspace need to 'fix' webfonts?
No. First, because many foundries' license agreements would not allow hosting webfonts in TTF format anyway. Second, because IE9 accepts webfont formats other than TTF so that IE9 does not need webfonts in TTF format. And third, because IE9 is as generous as any other browser when it comes to 'embedding bits' of non-TTF webfonts. The implementation scenario sketched below may clarify this a bit more.
HTML
Adding, as suggested by Paul Irish, the following meta tag to the HTML header (in combination with a proper <!DOCTYPE> directive) makes IE9 use its latest rendering mode which supports WOFF webfonts:
<meta http-equiv='X-UA-Compatible' content='IE=edge,chrome=1'>
Both Microsoft and Google provide more detailed information on this.
CSS
Ethan Dunham's version of a cross-browser @font-face declaration provides every browser with the webfont format it needs:[2]
@font-face {
     font-family: 'MyFontFamily';
     src: url('myfont-webfont.eot?iefix') format('eot'),
             url('myfont-webfont.woff') format('woff'),
             url('myfont-webfont.ttf') format('truetype'),
             url('myfont-webfont.svg#svgFontName') format('svg');
}
A quick overview of which browser picks which webfont format:
EOT, for IE 4–8.
WOFF, for IE 9+, Firefox 3.6+, Chrome 6+, Blackberry 6+, Opera 11.10+.
TTF, for Opera 10+, Safari 3.1+, iOS 4.2+, Android 2.2+.[3]
SVG, for Safari, iOS.
Embedding bits
Of the webfonts offered in this scenario's @font-face declaration, none needs to have 'embedding bits' set to 'installable'. All browsers accept WOFF, EOT, SVG, and (with exception of IE9) TTF webfonts even if their 'embedding bits' are not set to 'installable'. And in this scenario, IE9 will pick the WOFF format. Neither type foundries nor webfont licensees need to bother about 'embedding bits'.

[1] The 'embedding bits' refer to fsType information in the OS/2 table, and 'installable' means that all fsType bits are off. And TTF refers to TTF and OTF.
[2] I prefer this cleaner solution over the one offered in a more recent article, because in combination with above-mentioned meta tag it should have the same effect in IE9.
[3] Please note that many if not most type foundries do not allow hosting TTF or OTF webfonts and usually provide WOFF, EOT and maybe SVG. It should be evident, though, that these three address almost all major browsers.

All texts & images, unless noted otherwise:
Copyright © Karsten Luecke
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