ysoserial.net is a deserialization payload generator designed for .NET applications and frameworks. The tool creates malicious payloads that exploit deserialization vulnerabilities in various .NET formatters including BinaryFormatter, SoapFormatter, and NetDataContractSerializer. It generates serialized objects that can execute arbitrary code when deserialized by vulnerable .NET applications, making it useful for penetration testing and security research. The tool supports multiple .NET serialization formats and can be used to test applications for insecure deserialization flaws that could lead to remote code execution.