Update on the Compatibility View List in Internet Explorer 8


Internet Explorer Team Blog

Update on the Compatibility View List in Internet Explorer 8

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I’ve written a few posts about the Microsoft-supplied Compatibility View List on the IEBlog, calling out the what, how, and why of the feature. I wanted to take this opportunity to bring the community up to speed on what’s transpired since Internet Explorer 8 released back in March of this year and talk a little bit about the future actions planned for the list.

The Story So Far…

Let’s start with a quick recap of the feature... by default Internet Explorer 8 displays web content using its newest, most standards compliant mode. The problem is that some of today’s web pages expect the older, less interoperable behavior from Internet Explorer , handing this latest version of Internet Explorer code meant for older releases of the browser. The result is web pages that might not function correctly in ways ranging from just looking a bit misaligned to not working at all. During the Beta cycle, we introduced the Compatibility View button, which allowed savvy end-users to resolve compatibility problems they might encounter as described above. Despite all of our activities around site outreach, we saw telemetry data that indicated users still had to use Compatibility View in the course of normal browsing. Of particular concern was button use on popular / critical (banking, government, etc…) sites that users rightfully expected to “just work” in Internet Explorer 8. To give users the best possible experience, we combined telemetry data about Compatibility View button presses with other feedback sources – customer-filed bugs, Report a Webpage Problem data, our own compatibility testing, etc… - to create a list of sites that were likely best displayed in Compatibility View. The list’s not enabled by default - users must opt-in to the feature (known simply as the Compatibility View List or Compatibility List, in other documents) as part of the first run experience or later by selecting ‘Include updated website lists from Microsoft’ at Tools -> Compatibility View Settings. For those that chose to do so, Internet Explorer 8 displays sites on the list in Compatibility View rather than the default “best standards mode”. In other words, it’s as if the user pressed the Compatibility View button for sites on the list with the benefit that the end user avoids having to first experience a website compatibility failure to make the determination that these particular sites are best viewed in a non-default manner. You can view the list currently available on your Internet Explorer installation by typing ‘res://iecompat.dll/iecompatdata.xml’ into the browser’s address bar.

Compatibility View List Updates Since Internet Explorer 8’s Release

Though the originally stated list update frequency was about every two months, we’ve actually kept a brisker pace, delivering an updated list about every month. There are a few reasons a faster cadence immediately following Internet Explorer 8’s release has made sense –

  • To be extra-responsive to end-user and site administrator feedback. The Compatibility View List is still relatively new and we wanted to be as agile as possible in responding to list edit requests.
  • To align with Windows 7’s Release Candidate build. The Internet Explorer team shipped a Compatibility View List update in May specifically to coincide with Windows 7’s Release Candidate; prior versions of the Compatibility View List were only available for Windows XP and Windows Vista (and corresponding server versions).

Going forward, we expect to return to the originally stated cadence. A spreadsheet, available from the Microsoft Download Center, provides transparency into the changes that have been made to the list since its creation. The spreadsheet also contains targeted guidance for sites on the list including step-by-step instructions for performing compatibility testing with and without the Compatibility View List active and the list removal process.

Changes to the Site Removal Process in Upcoming Compatibility View List Updates

Since the list’s inception, the criteria for site removal has been site owner request (process documented here). Going forward, we’re adding a second way that sites can get removed from the Compatibility View List: basic user experience testing.

For several months now, the Internet Explorer team has been doing basic user experience testing for all sites listed on the Compatibility View List. The test methodology is straightforward: in each test pass a tester starts at the home page of a site and examines a set of pages that follows the core user experience for that website. For example, on a video sharing site the core scenarios include watching a video, rating a video, commenting on a video, sharing the video link with a friend, etc… and the tester will browse around the site completing each operation. On each page visited, testers check for visual and functional issues by performing comparisons between Internet Explorer 8 modes (Internet Explorer 8 Standards and Compatibility View) and between browsers. Doing these comparisons aids in determining what working / not working looks like, which isn’t always obvious on sites / pages the tester isn’t super-familiar with. A grading system tracks the type and severity of problems, ranging from ‘no problems found’ to ‘scenario doesn’t work’. Subsequent test passes combine revisiting pages that were previously identified as having compatibility issues as well as augmenting with new pages.

The question of how much of a site one needs to test to determine compatibility is a difficult one. While it's somewhat straightforward to prove the presence of a compatibility problem, it’s decidedly

less so to prove the absence of one. In other words, if a tester finds a compatibility problem, there’s a problem. But, if a tester doesn't find a compatibility problem, does that mean there isn't a problem or that the tester just didn’t visit a page that happens to demonstrate one? By charting the compatibility “scores” of the tested sites over time and by traversing a different set of pages in subsequent test passes, we’ve grown more confident in our ability to gauge the type of compatibility experiences Internet Explorer 8 users are likely to have independent of the Compatibility View List.


With the next Compatibility View List update you’ll see a new designation for site removal in the tracking spreadsheet – “Removed per Microsoft testing” - indicating that our test passes have not found a compatibility issue for some time and so we’re removing that site from the Compatibility View List. We’ve stated previously that we view the Compatibility View List as a short-term solution and believe that adding this additional site removal criteria helps us achieve this end while at the same time ensuring that users continue to have a great compatibility experience.

Scott Dickens
Program Manager

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