a card catalog of things you can run in your browser
languages
Python in your browser
CPython 3.14 via Pyodide.
C# in your browser
Roslyn on .NET WebAssembly.
Go in your browser
Yaegi interpreter in WebAssembly.
C and C++ in your browser
Real Clang in WebAssembly.
Rust in your browser (experimental)
Experimental: Miri interprets Rust.
tools
Regex in four languages
Python, C#, Go or C++ engine.
Test a regular expression with Python's re, .NET, Go's RE2 or C++ std::regex — each compiled to WebAssembly — and watch matches, groups and a substitution preview update live.
Format & validate JSON
Python, C#, Go or C++ engine.
Pretty-print, minify, sort keys, validate and explore JSON with Python, .NET, Go or a hand-written C++ parser, all in WebAssembly in your browser. Healing almost-JSON is Python-only.
Markdown → HTML
Python, C#, Go or C/C++ library.
Convert Markdown to HTML with Python-Markdown, Markdig, goldmark or md4c, each compiled to WebAssembly, with a sandboxed preview and a safe mode.
Unified text diffs
Python, C#, Go or C++ engine.
Compare two blocks of text side by side with Python's difflib, DiffPlex, go-diff or a hand-written Myers diff in C++, each compiled to WebAssembly.