An F# Script file, identified by the .fsscript or more commonly the .fsx extension, is a source code file written in the F# programming language, which is a functional-first language on the .NET platform. Unlike standard .fs files that are meant to be compiled into permanent binary assemblies like DLLs or EXEs, .fsscript files are designed for interactive execution. They are processed by the F# Interactive (FSI) tool, allowing developers to run code snippets immediately without the need for a formal compilation step or project file. This format is highly valued for data science, financial modeling, and rapid prototyping because it supports the inclusion of compiler directives to reference external libraries and other scripts directly within the code. The file itself is stored in a plain text format, making it compatible with any text editor. Because F# is part of the ML language family, these scripts benefit from strong type inference, pattern matching, and a robust type system, enabling complex logic to be expressed concisely and safely within a scripting environment.