Free Online Compiler & Code Runner
Why Use FlexyPdf Compilers?
Docker Sandboxed
Every execution runs in an isolated container — no code ever touches the host system.
Instant Results
Results appear within seconds. No compilation queues, no waiting.
5s Timeout
Infinite loops are killed automatically. Your browser stays responsive.
Monaco Editor
VSCode-grade editor with syntax highlighting for every supported language.
Fully Working Compilers
LivePython Compiler
NEWWrite and run Python code online
JavaScript Runner
NEWRun JavaScript code online instantly
C++ Compiler
NEWCompile and run C++ code online
SQL Runner
NEWRun SQL queries online with SQLite
These 4 compilers execute code via sandboxed Docker containers. Requires the FlexyPdf backend server running locally.
How It Works
Write Your Code
Open any compiler page and type or paste your code into the Monaco editor. Syntax highlighting and auto-indent are active immediately.
Click Run
Press the Run button. Your code is sent securely to a local Docker container that compiles and executes it.
See the Output
stdout appears in the output console in green. Errors appear in red. The container is destroyed after every run.
Coming Soon
In DevelopmentJava Compiler
NEWCompile and run Java code online
TypeScript Compiler
NEWCompile and run TypeScript online
Go Compiler
NEWRun Go (Golang) code online
Rust Compiler
NEWCompile and run Rust code online
C Compiler
NEWCompile and run C code online
C# Compiler
NEWRun C# code online with .NET
Kotlin Compiler
NEWRun Kotlin code online
Swift Compiler
NEWRun Swift code online
PHP Compiler
NEWRun PHP code online
Ruby Compiler
NEWRun Ruby code online
R Compiler
NEWRun R code online for data science
Scala Compiler
NEWRun Scala code online
Groovy Compiler
NEWRun Groovy code online
Dart Compiler
NEWRun Dart code online
Julia Compiler
NEWRun Julia code online
Haskell Compiler
NEWRun Haskell code online
Elixir Compiler
NEWRun Elixir code online
Erlang Compiler
NEWRun Erlang code online
Perl Compiler
NEWRun Perl code online
Lua Compiler
NEWRun Lua code online
Bash Runner
NEWRun Bash shell scripts online
PowerShell Runner
NEWRun PowerShell scripts online
Assembly Compiler
NEWWrite and run Assembly code online
Objective-C Compiler
NEWRun Objective-C code online
Fortran Compiler
NEWRun Fortran code online
COBOL Compiler
NEWRun COBOL code online
What is an Online Compiler?
An online compiler is a web-based tool that lets you write, compile, and run source code directly in your browser — without installing any programming language, IDE, or runtime on your computer. FlexyPdf's online compiler collection covers 30 programming languages, from widely-used languages like Python, JavaScript, and C++, to specialized ones like Haskell, COBOL, and Erlang.
How FlexyPdf Compilers Work
Every time you click Run, your code is sent to the FlexyPdf backend server which spins up a fresh Docker container, copies your code file into it, compiles or interprets it, captures stdout and stderr, then destroys the container. The entire cycle takes 1–5 seconds depending on the language. Memory is limited to 128 MB and CPU to 1 core, and a 5-second hard timeout prevents runaway programs. No code or output is stored after execution.
Benefits of Online Code Compilers
Online compilers remove the setup barrier entirely. Learning a new language no longer requires spending 30 minutes installing an SDK, configuring environment variables, and finding the right IDE. You open a browser, type code, and see it run. This makes online compilers invaluable for students, educators, developers testing small snippets, interviewers running coding challenges, and anyone who needs to quickly verify an algorithm.
Supported Languages and Runtimes
FlexyPdf currently provides fully operational execution for Python 3.11, Node.js 20 (JavaScript), GCC 13 (C++17), and SQLite (SQL). In development: Java, TypeScript, Go, Rust, C, C#, Kotlin, Swift, PHP, Ruby, R, Scala, Dart, Julia, Haskell, Elixir, Erlang, Perl, Lua, Bash, PowerShell, Assembly (NASM), Objective-C, Fortran, and COBOL.
Frequently Asked Questions
Which programming languages are supported?
FlexyPdf currently offers compilers for 30 languages: Python, JavaScript, C++, SQL, Java, TypeScript, Go, Rust, C, C#, Kotlin, Swift, PHP, Ruby, R, Scala, Groovy, Dart, Julia, Haskell, Elixir, Erlang, Perl, Lua, Bash, PowerShell, Assembly, Objective-C, Fortran, and COBOL. Python, JavaScript, C++, and SQL are fully operational today.
Are the compilers free to use?
Yes — completely free with no sign-up, no watermarks, no usage limits, and no hidden fees. Run as many programs as you need.
How is security handled?
Code runs in an ephemeral Docker container with memory (128 MB) and CPU (1 core) limits, a 5-second hard timeout, and no network access. The container is permanently deleted after each execution.
Can I use third-party libraries or packages?
Not yet — the current environment supports each language's standard library only. Package manager support (pip, npm, cargo) is on the development roadmap.
Does it work on mobile?
Yes — all compiler pages are fully responsive. The Monaco editor works on tablets and large-screen phones, though a desktop is recommended for the best coding experience.
Do I need Docker installed locally?
Only for code execution. The Monaco editor and all UI run in the browser. To execute code you need the FlexyPdf backend server running locally with Docker available on the host machine.