With Windows 10, Microsoft will be releasing Project Spartan, a new browser across all Windows 10 devices, from phones to tablets, PCs and beyond. They have now built a new rendering engine focused on interoperability with other modern browsers. While creating a modern rendering engine, they didn’t want to break the web. They tested their new rendering engine with top websites on the web. And they had a different approach to compatibility with the Web at large:
- Legacy vs. modern. While we were pushing ahead with new HTML5 features, we were also expected to preserve compatibility with old versions of IE, particularly for enterprise Web apps. Limited compatibility was provided through document compatibility modes within Trident, however compatibility could not be guaranteed and it provided consistent obstacles towards fixing long-standing IE-specific behaviors. Furthermore, fixing long standing interoperability bugs with other modern browsers could actually break sites who have coded to the IE-specific behavior.
- CV list. Our compatibility pass rates were dependent on the presence of the compatibility view list. This allowed us to “fix” broken sites by forcing them into old document modes which emulated legacy IE behaviors. However, this approach requires testing and maintenance, and doesn’t scale well beyond the top sites.
- X-UA-Compatible. Some sites forced an older document mode using the “x-ua-compatible” header. However, rather than using it as a temporary stopgap, they would rely upon that to keep that version of the site working in future versions of IE while they developed an evergreen code path of their site for other modern browsers.
- Standards focus. Our focus on building new HTML5 features was to comply with Web standards, which in turn should lead to interoperability among browsers. However, interpretations of the standards document could easily vary, leading to real-world interoperability gaps and ultimately more bug fixing for Web developers and more broken sites for customers.
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Source: IE Blog