Why Can\'t Internet Explorer 7, 8, and 9 Load EOT Fonts Over HTTPS?

Cross-Browser Font Embedding with HTTPS: Resolving the IE @font-face EOT Loading Issue

One of the key challenges encountered when embedding fonts using @font-face is ensuring compatibility across different browsers. While most browsers support the various font formats, Internet Explorer 7, 8, and 9 exhibit a peculiar behavior when accessing EOT fonts over HTTPS.

The issue arises when attempting to load the EOT font via HTTPS, while the HTML page containing the @font-face declaration may be hosted on either HTTP or HTTPS. In such scenarios, Internet Explorer simply fails to load the EOT font, even though it works seamlessly over plain HTTP.

To delve into the underlying cause, it is crucial to examine the server hosting the font. In most cases, the server should send an appropriate content-type header, namely "application/vnd.ms-fontobject," for the EOT font file.

The problem arises when the HTTP header Cache-Control is set to "no-cache" for the font. This setting, while acceptable in an HTTP environment, causes Internet Explorer to disregard the downloaded font over HTTPS.

The most likely explanation for this behavior is that it resembles the behavior described in KB 815313, which addresses preventing caching when downloading active documents over SSL. Consequently, if the "Cache-Control" header exists and is set to "no-cache," removing it should resolve the issue.

Therefore, if you observe Internet Explorer progressing through the font options in the Developer Tools network view without loading the EOT font over HTTPS, verifying the "Cache-Control" header and removing it may be a potential solution. By addressing this nuance, you can ensure consistent font embedding across browsers, even when accessing the fonts over HTTPS.

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