Phasing out CMS support for IE11

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This post outlines the drivers and timeline for phasing out Silverstripe CMS support for Internet Explorer 11 in the near future.

1. Summary

Key drivers for dropping support of IE11 include:

  • Microsoft have communicated their own plans to phase out support
  • According to web metrics the browser continues to see a decline in usage
  • Current support for IE11 is not optimal - leading to a bad user experience
  • Reduce the overall CMS maintenance burden, reprioritising maintainer focus

The phase out approach will involve:

  • CMS 4.9 will be the final version to provide support for IE11
    • This version is to be released in September 2021
  • CMS 4.10 will not commit to support IE11. Release date is still to be confirmed - although will be within the period between December 2021 - March 2022

Please note, these support commitments only apply to those accessing Silverstripe CMS admin interface. Websites built with Silverstripe CMS are unaffected by this proposal and are managed at a project level.

Also note, the non-Chromium (legacy) Microsoft Edge is already deemed out of support by Microsoft and is not supported by Silverstripe CMS.

2. Drivers for dropping support

Microsoft are phasing out support of IE11

It’s worth acknowledging that IE11 usage percentages could very likely be attributed to 100% usage within some organisations who are locked to certain distributions. It’s also worth pointing out that IE11 has been in the past known to be relied on by users of assistive technologies, given the browser’s high-level of support for tools like JAWS, Dragon NaturallySpeaking and Zoomtext. It’s difficult to obtain accurate figures for all assistive technology users, but the Webaim Screen Reader Survey from 2021 records that approximately 3.3% of respondents use a screen reader with Internet Explorer 11 (mainly JAWS), down from 12.5% in 2019.

The above has been considered in the context of how Microsoft plans to support IE11. Recent announcements from May 2021 confirm that:

While it is acknowledged that usage of IE11 may still persist beyond Microsoft’s official support of the browser, support for Silverstripe CMS is taking influence from Microsoft’s own timelines.

Current state of IE11 usage

As at June 2021, IE11 usage world-wide is below 1% according to the following three source of metrics:

Notably, Silverstripe’s NZ-based Government platform still sees 4% of CMS requests use IE11. Of these, the average use per project is 3% of total CMS requests, an indicator of low reliance.

Current CMS support for IE11 is not the focus of CMS maintainers

New CMS features and every quarterly CMS release are put through a full manual regression test on the IE11 browser to confirm that all functionality can be performed as expected.

However for better or worse, based on usage statistics, prioritising time to resolve IE11-specific compatibility issues in the CMS is lower than on other, more popular browsers. Issues that prevent a task from being completed will be triaged for resolution, but we still see lower impact issues that come at a cost of the user experience, like: “Select a content type” overlaps with dropdown field and Banner block contents are not vertically aligned in the center. These examples are likely compatibility issues with the CSS flexbox property where IE11 support is known to be infamously patchy. Where possible we will always encourage people using the CMS to use a browser other-than IE11.

Aiming to reduce the maintenance burden of Silverstripe CMS

Looking at the UX bugs noted previously, often IE11 compatibility issues will require a JavaScript polyfill to resolve. Implementing these polyfills that are specific to IE11 support add to the download size of each view in the CMS and over time contribute to slowing down their operation.

Maintainer onboarding and contributions to the CMS codebase should also be considered here. Understanding that any friction in this area has the potential to disincentive contributions, needing to know about the legacy frontend development constraints of supporting IE11 could very well impact this.

And with a longer-term view, with a high-level goal of creating new concurrent CMS UIs (via opt-in modules), these might have cross-dependencies to existing Javascript (e.g. for reuseable components), so the polyfills and other custom code required for IE11 might still prevent us from starting with a “clean slate” unless we remove IE11 support for the existing CMS UI as well.

3. Phase out timeline

CMS 4.9 release

The final CMS version to claim compatibility support for IE11 will be CMS 4.8. This version is planned to be released in September 2021.

Following the standard Silverstripe CMS support timeline, this version will stay in limited support for six months after a subsequent CMS 4.10 release is made. This will see CMS 4.9 in limited support up until at least June 2022 - when Microsoft will shut down support for IE11.

CMS 4.10 onwards

CMS 4.10 will not commit to support IE11. This version will not be required to be tested by CMS maintainters on IE11 prior to its release. While there are no immediate plans to do so, IE11-specific polyfills that have been added in the past for bug fixes and features will be removed from the codebase as required.

The release date of CMS 4.10 is still to be confirmed, however it will fall within December 2021 and March 2022, following the existing quarterly release cycle.

Changes to affect CMS-support only

This information is specifically focused on IE11 support for Silverstripe CMS use, i.e the admin interface. Changes made as a result of this will not have an effect on the compatibility of IE11 with the front-end of web projects which is a decision and responsibility of the project development team…

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