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Web

--target web and --target wasm are aliases for the same backend. Both produce a self-contained HTML file with embedded WebAssembly and a JavaScript bridge for DOM widgets.

perry app.ts -o app --target web    # same output as --target wasm
open app.html

See WebAssembly / Web for the full documentation: how it works, supported features, UI mapping, FFI, threading, limitations, and examples.

Why one target instead of two?

Perry used to have two browser backends:

  • --target web (perry-codegen-js) — transpiled HIR to JavaScript
  • --target wasm (perry-codegen-wasm) — compiled HIR to WebAssembly

These were consolidated into the WASM target so browser apps get near-native performance, FFI imports, and Web Worker threading without needing a separate JS-emit pipeline. The DOM widget runtime that the old --target web provided is now embedded in wasm_runtime.js. Both flags route through perry-codegen-wasm and produce identical HTML output.

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