All JIRA Upgrade Guides (version 3.x and later)
This page lists the upgrade guides from JIRA versions 3.x and later. You can also view the aggregated upgrade guides from JIRA versions 3.x and later (warning: the aggregated upgrade guides page is big!).
If upgrading from a previous version of JIRA please pay attention to the Upgrade Guide of the version you are upgrading to, and any version of JIRA that you are 'skipping' during the upgrade.
You may be interested in the list of release notes from JIRA versions 3.x and later.