Server: Atlassian JIRA, version from 4.2 to 6.2+, including JIRA OnDemand. (Please use JIRA Client 3.0.2 with JIRA 5.1.8 and older versions.)
Additional server Authentication: Basic HTTP, Digest, NTLM version 1 or NTLMv2.
Operating System: Microsoft Windows (XP/Vista/7/8), Linux/x86 or AMD64, Apple Mac OS X (Leopard/Snow Leopard/Lion/Mountain Lion/Mavericks), or any other that supports Java 6.
System Memory: 256 MB required, 512 MB recommended.
Hard Drive Space: 150 MB required, 300 MB recommended.
Screen Resolution: 1024x768 or better.
Displays: multiple displays are supported, but JIRA Client should be restarted when a display is connected or disconnected.
Network Connection: Atlassian JIRA produces a lot of traffic when answering JIRA Client requests, so performance over slow network connection may be degraded. (Hint: turn on "Use Gzip Compression" setting in JIRA configuration to reduce traffic.)
Java: If you downloaded a distribution without bundled Java, you need Java 6 or later available at java.com.