Go Browser Interpreter (WASM + Yaegi)

Run Go code directly in your browser using WebAssembly, Yaegi, and the Monaco Editor (VS Code editor).

No backend. No server logic. Just Go + WASM.

What is this?

This project is a client-side Go playground that lets you:

• Write Go code in a real code editor (Monaco / VS Code)
• Run the code instantly
• See output in a terminal-like panel

Everything runs inside the browser. Your code is interpreted locally. No data is sent to any server.

How does it work? (Conceptual)

graph TD;
    Browser[Browser HTML + JS] -->|Sends Code| WASM[Go Compiled to WebAssembly];
    WASM -->|Executes| Yaegi[Yaegi Interpreter];
    Yaegi -->|Interprets| User[User Go Code];
    Yaegi -->|Returns Output| Browser;

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1. JavaScript collects Go code from the Monaco Editor.
2. Go (compiled to WASM) receives the code.
3. Yaegi interprets and executes the Go code.
4. Output is sent back and displayed in the browser.

Features

Editor (Monaco)

• Go syntax highlighting
• Line numbers & auto-indent
• Dark theme
• Auto-focus on load
• Ctrl + Enter / Cmd + Enter to run
• Same editor used by VS Code

Runtime

• Runs fully in the browser (WASM)
• Real Go execution via Yaegi
• Real goroutines & channels (no fake scheduler)
• Supports goroutines, channels, maps, slices, functions

Known Limitations (Expected)

This is not the official Go Playground. By design:

• No networking (HTTP / TCP disabled)
• No file system access (WASM sandbox)
• No fake time acceleration (time.Sleep behaves normally)

These are browser + WASM limitations, not bugs.

Project Structure

.
├── main.go        # Go → WASM + Yaegi interpreter
├── main.wasm      # Compiled WebAssembly binary
├── index.html     # UI + Monaco Editor + JS glue
├── style.css      # Page styling
├── wasm_exec.js   # Go WASM runtime (required)
├── go.mod         # Go module & dependencies
└── README.md      # This file

How to Run Locally

1. Requirements

• Go 1.24+ (Required for latest WASM support)
• modern browser (Chrome, Firefox, Edge)
• A local web server (e.g., Python, Node, or serve)

2. Initialize Dependencies

If you are running this for the first time, download the required Yaegi packages:

go mod init go-browser-interpreter
go get [github.com/traefik/yaegi/interp](https://github.com/traefik/yaegi/interp)
go get [github.com/traefik/yaegi/stdlib](https://github.com/traefik/yaegi/stdlib)

3. Build the WASM file

Compiles your Go code into a .wasm binary that the browser can understand.

GOOS=js GOARCH=wasm go build -o main.wasm main.go

Optional (Optimization):

To reduce file size, strip debug information:

GOOS=js GOARCH=wasm go build -ldflags="-s -w" -o main.wasm main.go

4. Copy Go WASM runtime

You must copy the JavaScript glue code provided by your Go installation. For Go 1.24+ / 1.25+:

cp "$(go env GOROOT)/lib/wasm/wasm_exec.js" .

(Note: If the above fails, try $(go env GOROOT)/misc/wasm/wasm_exec.js)

Then confirm:

ls -l wasm_exec.js

5. Start a local server

Browsers will not load WASM files from the file system (file://) due to CORS security policies.

Using Python:

python3 -m http.server 8080

Open in browser: http://localhost:8080

Credits

• Go Team — WebAssembly support
• Traefik Labs — Yaegi interpreter
• Microsoft — Monaco Editor