Support for SHA-2 has improved over the last few years. Most browsers, platforms, mail clients, and mobile devices already support SHA-2. However, some older operating systems such as Windows XP pre-SP3 do not support SHA-2 encryption.
We encourage users running older, less secure systems to upgrade.
This page lists the minimum version required for SHA-2.
Browser SHA-2 Support
|Browser||Minimum Browser Version|
|Internet Explorer||6+ (With XP SP3+)|
|Safari||3+ (Ships with OS X 10.5)|
Operating System SHA-2 Support
|Operating System||SSL Certificate Minimum OS Version|
|Mac OS X||10.5+|
Above information is excerpted from Digicert.com