When a new version of Confluence is released, it is sometimes necessary for Confluence to convert older data to a newer format. This is done by a series of 'upgrade tasks' which Confluence runs on the data.

Newer versions of Confluence don't always contain all the upgrade tasks needed to convert data from the very oldest versions of Confluence, so sometimes upgrades from very old versions must be performed in several stages. Exact changes between older, non-supported versions and current versions aren't always documented.

If you're upgrading Confluence and plan on jumping several versions, you should always read the release and upgrade notes to help you plan your upgrade. Depending on your configuration, you may need to upgrade to interim versions to ensure your upgrade is as smooth as possible. You should also check the relevant supported platforms. We add and remove support for platforms as we progress, so for example, your current database may not be supported in a newer version.

To find out more about changes in each release, see:

• Confluence リリース ノート
• Confluence upgrade notes