Web font service Typekit has warned against relying too much on emulated older versions of Internet Explorer for cross-browser testing using Browser Modes.
The Browser Modes feature, included in IE9/10's developer tools, aims to make testing simpler by emulating how a website would render in a previous version of the browser, such as IE7 or 8.
According to Adobe's cloud-based service’s tests, these emulated testing environments create "more trouble than benefit because they behave differently than real copies of IE7 and IE* would," said the company in a blog post.
By way of example, the Typekit post explained how IE9’s Browser Modes for IE7 and IE8 render web fonts. Instead of correctly dealing with multiple weights or styles when such things are present, the emulated versions of IE “pick the first @font-face rule in the style sheet and use that weight for all text on the page set in that font family”.
A common symptom, according to the post, is seeing all text for a face in italic, since it's before ‘normal’ in the alphabet, and Typekit orders @font-face rules alphabetically.
The post encouraged testing in full installs of IE or using an online service that does the same, such as BrowserStack. Ironically, considering Adobe’s ownership of TypeKit, Adobe recently and abruptly shut down a tool that would have assisted with such testing.
On March 13, BrowserLab was closed (opens in new tab), which senior product manager Bruce Bowman blamed on a dramatically changing landscape and Adobe's focus being on "new solutions", such as Edge Inspect for mobile. Bowman recommended BrowserStack and Sauce Labs as other options.