Mattermost is dropping support for Internet Explorer (IE11) in v5.16

Why is Mattermost dropping IE11 support?

Since IE11 only receives security updates and compatibility fixes by Microsoft, it has not kept pace with evolving web standards as other browsers have. We have reached the point where, to continue the improvement and forward progress of the Mattermost web app, it is necessary to make use of technologies which are not supported (and never will be supported) by IE.

For specific examples of areas currently hindering development, see

Moreover, below is a list of deprecations in the wider world:

  1. IE11 is a legacy browser. Although Microsoft will continue to support it until Windows 10 EOL, it is deprecated in favor of Microsoft Edge.
  2. Microsoft considers that it should only be used “for compatibility with legacy intranet systems” and, wherever possible, a modern browser such as Edge should be used for all other Intranet/Internet resources.
  3. Slack ended IE11 support on March 15, 2019.

How do I prepare?

If you use another supported browser (Chrome, Firefox, Safari or Edge), or the Mattermost Desktop Apps, you do not need to make any preparations. See our documentation for supported browser versions.

If you are using IE11, we recommend you to install the Mattermost Desktop Apps, available on Windows, Mac and Linux, or downloading one of the supported browsers. See install instructions below for each option:

If your organization relies on IE11 for any reason, Mattermost offers a fully functional desktop application where using an alternative web browser to access Mattermost is not an option. To assist an organization with a wide deployment of the desktop application, an MSI installer for Windows is scheduled to release as Beta in August, 2019.

When is this happening?

Support for IE11 will be dropped in Mattermost v5.16, which releases on October 16, 2019.

Security updates for the latest scheduled Mattermost release supporting IE11, v5.15, will continue to be made until December 15, 2019. This follows Mattermost’s security policy of backporting security fixes to the previous two monthly releases.

The last ESR (Extended Support Release) with IE11 support, Mattermost v5.9, will continue to receive security updates and major bug fixes for the length of its lifecycle. See our documentation for more information about the ESR.

Questions or concerns?

Let us know by replying to this forum post, or contacting us at