The algorithms used to generate Authorization Codes for SketchUp Pro 2015 are proprietary. Sites claiming to have a "Keygen" (Key Generator) are often distributing malware. Because legacy software like SketchUp 2015 might have unpatched security vulnerabilities, these malicious programs can compromise your system, steal data, or install ransomware.
If you have a legitimate perpetual ("Classic") license for SketchUp Pro 2015, your activation details are found in your original purchase confirmation email. Look for emails from sketchupmail@sketchup.com . Sketchup Pro 2015 Serial Number And Authorization Code
to look up your details by entering the email address used for the purchase. Within the App The algorithms used to generate Authorization Codes for