F# Online Compiler
Write, compile, and run F# code online directly from your browser with our free Online F# Compiler. Practice functional-first programming, pattern matching, functions, collections, and .NET-based logic without installing Microsoft Visual Studio or configuring the .NET SDK locally.
How to Use This F# Compiler
- Write or paste your F# code
Enter your program in the Code Editor. You can test variables, functions, lists, records, pattern matching, pipelines, recursion, and other F# features supported by the execution environment. - Click the Run button
Select Run to compile and execute your F# code. If your program contains a syntax, type, compilation, or runtime error, review the returned feedback, correct the relevant code, and run it again. - Check the Output screen
Your program result and compiler messages appear in the Output panel. Use the available controls to copy, download, or delete the output before testing another F# program.
Key Features
- Free Online F# Compiler: Write and execute F# programs directly from a modern web browser.
- Zero Installation: No need to install Visual Studio or configure a local .NET SDK for supported programs.
- Fast .NET Execution: Test F# logic using the configured .NET execution environment.
- Instant Feedback: Click Run and quickly review program output or compiler errors.
- Functional-First Programming: Practice immutable values, higher-order functions, recursion, pipelines, and function composition.
- Pattern Matching: Experiment with one of F#’s core features for handling values, tuples, lists, records, and discriminated unions.
- Dark and Light Mode: Switch the Code Editor theme for comfortable coding in different environments.
- Output Controls: Copy, download, or clear generated output directly from the Output panel.
1. How do I print output in F# using printfn?
F# commonly uses printfn to print formatted output followed by a newline.
You can also print variables with format specifiers:
Enter the code in the Code Editor, click Run, and check the result in the Output screen.
2. Do I need to install Visual Studio or .NET to use this online compiler?
No. You can use this Online F# Compiler directly from your browser without installing Visual Studio or setting up the .NET SDK locally for supported programs.
A local .NET development environment may still be preferable for larger applications, NuGet packages, advanced debugging, multi-project solutions, or software requiring unrestricted filesystem and system access.
3. Is F# a purely functional programming language?
F# is best described as a functional-first, multi-paradigm programming language. It strongly supports functional programming while also allowing object-oriented and imperative programming when needed.
For example, a functional pipeline can be written as:
This makes F# useful for developers who want functional programming features while remaining within the .NET ecosystem.
4. Does this compiler support F# functions and pattern matching?
Yes. Functions and pattern matching are fundamental F# features and can be tested in standard F# programs.
You can also define reusable functions:
Support for external NuGet packages or specialized .NET libraries may depend on how the online compiler environment is configured.