Do not search for "cracked" or "torrent" versions. Those are illegal, often contain malware, and violate CCDC's licensing. The official free version is perfectly capable for visualization and basic crystallography needs.
Here is the breakdown of how you can access Mercury for free: ccdc mercury free download
In recent years, the CCDC has rolled out web-based access. This allows users to access Mercury functionality directly through a browser without downloading any software. This is the ultimate "free download" because there is no installation required. It is accessible via the CCDC website and is perfect for quick visualization checks. Do not search for "cracked" or "torrent" versions