We default to supporting the newest and the last previous two
popular browsers (Edge, Safari, Chrome, Firefox, and Android Browser) for
mobile and desktop devices. We also support Internet Explorer 11 but not older
versions of Internet Explorer, as Microsoft no longer supports these
Older versions are much harder, more time consuming and hence more expensive to
design for, develop for and support.
In limited special cases, user demographics will dictate that supporting a less
common or older version of a browser is required. Those special cases should be
identified early on so we can plan for additional time and expense in order to
support the version.
Browser support means that we make a site or web app usable. A usable site
allows a user to achieve all necessary tasks.
Support does not mean visual and behavioral parity across all browsers.
While we may strive for this, it's not always possible to achieve the exact
same user experience cross-browser.