This issue evolved over time and eventually we decided to change terminology to adapt to the practical reality of browser support in Moodle today:

User guidance (will be in release notes and so on)

Moodle is compatible with any standards compliant web browser. We regularly test Moodle with the following browsers:

Desktop:

• Chrome
• Firefox
• Safari
• Edge
• Internet Explorer

Mobile:

• MobileSafari
• Google Chrome

For the best experience and optimum security, we recommend that you keep your browser up to date. https://whatbrowser.org

Note: Legacy browsers with known compatibility issues with Moodle 3.2:

• Internet Explorer 10 and below
• Safari 7 and below

Developer guidance:

Developers are encouraged to embrace modern web technologies when a feature has been implemented by all major vendors (Chrome/Firefox/Edge/Safari). We encourage our users to run on up to date browsers, developers should focus the bulk of their attention on supporting these users when implementing new functionality.

Questions to ask, when deciding can I use 'feature-x'?

• What is the impact of this feature not being available?
  • If it breaks the site, you must ensure it is available in firefox/chrome releases over the last 1y and Safari/IE releases not mentioned in our compatibility issues
  • If it's just 'nice to have' cosmetic issue you do not need to be strict
• Is it supported by all major vendors on all platforms?
  • If not: You can't use this feature yet

Original description:
The browser version landscape has changed and we need to update our supported browser policy to reflect this.

Microsoft have moved to a continuous update model with IE11 / IE Edge and no longer support older versions on any version of windows. We should not either.

We currently list very old versions of the other browsers, but do not test on them (automated tests included).

We have technical reasons for not supporting older browser versions, especially for 3.2 which introduces a new theme - using bootstrap 4 which does not support old browsers. 3.2 also immediately follows an LTS release so it is a good time to be aggressive.

Review the current browser statistics page and come up with a new base line for the list of supported browsers.

Desktop

Internet Explorer - Edge + 11
Safari - 8+
Firefox - 44+
Chrome - 44+

Mobile

Chrome - 51+
IOS Safari - 8+

For reference here is the list of supported browsers for Moodle 3.1

Google Chrome 30.0 Latest
Mozilla Firefox 25.0 Latest
Apple Safari 6 Latest
Microsoft Internet Explorer 9 Latest Version 10 is required for drag-and-drop upload of content from outside the browser into Moodle