Installation and Upgrade > Installation and Configuration Guide - Update Existing Installation > Planning Before Updating an Installation > Types of Windchill Releases
  
Types of Windchill Releases
The application of code corrections is part of the normal maintenance of your system. PTC provides maintenance for Windchill products and applicable third-party applications via the following release vehicles:
Release Type
Content and Changes
Critical Patch Sets (CPS)
• Critical customer fixes
• Critical security fixes
• Upgrade fixes
• Qualification or certification of additional CAD tool releases
• Qualification or certification of client 3rd party components (for example, new browser releases, or Java updates)
Maintenance Releases
• The latest Critical Patch Set
• Minor perfective maintenance features
• New optional modules to add to your installation
Major Releases
• All content from previous maintenance releases
• New features and content
• Platform updates
• User interface changes and improvements
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Major releases may require upgrading your installation.