Compatibility/IE11

Summary
Future software features and improvements developed for MediaWiki by the Wikimedia Foundation will not support IE11. IE11 requires using a different, older JavaScript implementation standard version from all other major modern browsers, and the development cost to write everything in this older implementation standard is too great to sustain. Existing JavaScript software features will continue to appear and function normally for IE11 users, but over time we will be dropping support on a feature-by-feature basis.

Background
The past decade has been a time of constant, almost-overwhelming change in the world of front-end Web development. We’ve seen a massive increase in browser capabilities, a proliferation of new form-factors, and sweeping changes in HTML, CSS, and JavaScript themselves. By and large, these capabilities are improvements that make it easier to create lightweight, accessible and interactive features for our users.

As new standards emerge we have been very conservative about adopting them, because reliability of time-tested technology is fundamental to our mission and because it is not practical to run the new capabilities on older, cheaper or low-connectivity devices. Accessibility is a huge part of what we do and we tend to support browsers and systems well after most for-profit companies would have limited service, even when it means developing the same feature twice.

From time to time, and with heavy hearts, we have turned off full-support for browsers that have fallen below a certain usage percentage. This means that they can use the site, but it is a sub-optimal experience. Internet Explorer (or IE) is beginning to enter that realm. IE is a dying browser with shrinking usage. Microsoft has a new browser, Edge, which is based on Chromium, and Microsoft is actively encouraging users to move to Edge. We have already dropped full-support for all versions except for the last: IE11. Microsoft itself will be cutting off support for IE11 on its own services starting in mid-2021.

If it were just about usage, we would continue to support IE11 for another few years. However, IE11 is the last major Web browser that relies on ES5, a JavaScript version that came out in 2009. All other major browsers use ES6, a version of JavaScript that was released in mid-2015. As a result, our developers are limited to using ES5, which is harder to develop for and limits our feature capabilities. As you can imagine, this creates unwelcome challenges for what is already a small team, considering the size of the site we support. Beyond that, younger or newer developers joining the movement will often have to re-learn much of their craft, in order to write in ES5, adding additional hurdles to what is already a pretty challenging on-boarding process.

Decision
So we are going to stop developing new features in ES5, using the more efficient ES6. For now, the site will continue to function normally for IE users, it is just that new JavaScript-based features will not appear for them. Over time, as we start to upgrade or repair existing features, we might start to drop support for IE for individual features. We will notify you as that happens.

The cost
Again, nothing will change for existing users. They can still use Wikimedia-hosted projects and they can still use all existing features. But we might be soon getting to a point where an existing JavaScript feature needs to be rewritten and IE users will no longer have access to that feature.

As mentioned above, looking at pure usage numbers, IE11 is above our subjective threshold for turning off support entirely. While it is 0.9% of our traffic worldwide, it is as much as 11.8% of our traffic in specific countries. Here are some examples where it is high: Pakistan (11.8%), Iran (6.4%), Japan (4.2%), South Korea (5.1%). We will be monitoring traffic-share for IE in those countries as we debate lowering IE support further.

What's to be done
Nothing by you for now. You might hear from community members that they cannot access a new tool you have sent them to. Or, in the future, a user in your community might see a banner letting them know that a feature they were using is no longer available. Before we drop support for an existing feature we will notify you with a briefer message using similar channels. We wanted to give you this warning so that if you encounter any feedback from your community or see a communication from us about this in the future, you have this context.