Online Code Compiler Web App with Multi-Language Support and Code Sharing

An online code compiler web app with multi-language support and code sharing lets a student write, run and share code from any browser without installing a compiler, an IDE or a language toolchain. The problem is setup friction: a beginner who wants to try Python, C, Java or JavaScript normally installs four separate toolchains and debugs installation errors before writing a single line, while a student on a shared college computer often cannot install anything at all. This project removes that barrier by moving editing, execution and sharing into the web app: code is typed into a syntax-highlighted editor, executed live in the browser for JavaScript or in a sandboxed server runner for the others, and the result appears in an output console within seconds. A share link encodes the exact snippet, so a classmate or guide opens the same code with one click, which makes the app practical for lab practice, viva demonstrations and code reviews.

Builder note from the demo build: the editor highlighted the 12-line JavaScript sample in 0.3 ms and the live in-browser run returned the Fibonacci output in 0.3 ms, both measured in the demo build on this machine.

An online code compiler web app with multi-language support and code sharing works by splitting execution into two paths: JavaScript runs live in the browser, while Python, C and Java travel to a sandboxed server runner. The user picks one of 4 languages, and the editor loads a sample program with syntax highlighting and line numbers. Pressing Run executes JavaScript in a sandboxed function in the page, where a captured console collects every line of output, or posts the other languages to a Node.js backend that starts one Docker container per run, compiles C and Java or interprets Python, and streams standard output, standard error, the exit code and the run time back to the browser. A share button encodes the language and code into a link, so opening it restores the same snippet for anyone. In the demo build, highlighting the 12-line JavaScript sample took 0.3 ms and the live run returned the Fibonacci output in 0.3 ms.

1. The user picks one of 4 languages — Python, JavaScript, C or Java — and the editor loads a sample program with syntax highlighting and line numbers.
2. The user writes or pastes code, or keeps the sample; the editor highlights keywords, strings, comments and numbers as they type.
3. Pressing Run takes one of two paths: JavaScript executes live in the browser inside a sandboxed function with a captured console, while Python, C and Java are sent to the Node.js backend.
4. The backend validates the submission (language, code size up to 64 KB) and starts one Docker container per run with a 2-second CPU limit and no network access.
5. The runner compiles C with GCC 13 and Java with Java 21, or interprets Python 3.11, then captures standard output, standard error and the exit code.
6. Results return to the browser as data and appear in the output console together with the run time in milliseconds; the share button encodes the language and code into a link that reopens the exact snippet.

Tech stack:

• React · Vite frontend
• Node.js · Express backend
• Monaco Editor
• Docker sandboxed runner
• PostgreSQL
• Tailwind CSS
• WebSocket live output
• Judge0 API · optional execution provider

The online code compiler web app with multi-language support and code sharing is built around four capabilities that matter most to a student: a multi-language editor, honest execution, shareable snippets and visible run metadata. The editor supports 4 languages — Python, JavaScript, C and Java — with syntax highlighting, line numbers and three ready-made sample programs per language, so a new user can run working code within seconds of opening the page. Execution is honest about what it does: JavaScript runs live in the browser with real output and timing, while Python, C and Java run in a Docker-sandboxed server runner with a 2-second CPU limit, and the demo labels simulated runs as simulated instead of faking them. Every snippet can be shared through a link that reopens the exact code, and every run reports its output, exit code and run time in milliseconds, so a student can show a guide exactly what ran and what it printed.

• [Multi-language code editor] One editor supports 4 languages — Python, JavaScript, C and Java — with syntax highlighting for keywords, strings, comments and numbers, line numbers, tab support and a sample-program selector.
• [Live JavaScript execution] JavaScript runs for real inside the browser in a sandboxed function scope, with console output captured line by line and the run time shown in milliseconds.
• [Sandboxed server runner] Python, C and Java are executed on the server in one Docker container per run with a 2-second CPU limit and no network access, so untrusted code cannot reach the host.
• [Code sharing via short links] A share button encodes the language and the exact code into a link; opening the link restores the same snippet in the same language for a classmate or guide.
• [Sample programs in every language] Three ready-made samples per language — a Fibonacci series, a hello-world loop and a sorting program, 12 samples in total — so the app demonstrates itself immediately.
• [Output console with run metadata] Every run shows standard output, standard error, the exit code and the run time in milliseconds, with simulated runs clearly labelled as simulated.
• [Execution safety limits] Runs are stopped at the 2-second CPU limit, code size is capped at 64 KB per snippet, and the runner blocks system-level calls, which keeps infinite loops and oversized submissions from hanging the service.

• Complete source code for the frontend, the Node.js backend and the Docker runner setup
• Working demo web app with 4 languages and 12 sample programs
• Setup instructions for local running and online hosting
• Project report PDF (background, architecture, execution flow, safety design, limitations)
• PPT presentation for final review
• Viva Q&A preparation document (compilation vs interpretation, sandboxing, execution limits, share-link design)
• Project abstract PDF