7-Zip WASM

7-Zip compiled to WebAssembly, served as an offline-capable PWA on GitHub Pages. Compress, extract, inspect and test archives entirely in your browser — no uploads, no server-side processing, works offline after the first visit.

Features

• Create .7z and .zip archives (with optional password + header encryption for 7z)
• List, test and extract archives with paths preserved (7z, zip, tar, gz, xz, zst, rar, iso, …)
• Runs in a Web Worker — the UI never blocks on big archives
• Installable PWA with a versioned service-worker cache: every weekly build invalidates the cache automatically

File handling

When installed, the PWA doubles as a system-level archive handler. Everything here is feature-detected; browsers without support keep the plain dropzone/download behavior:

• Open with (desktop Chrome/Edge): file_handlers in manifest.webmanifest registers the app for the supported archive extensions; launched files arrive via window.launchQueue and open like dropped ones.
• Share sheet (Android Chrome): share_target receives shared files as a POST to ./__share, which the service worker intercepts, stashes in a dedicated cache and answers with a redirect; the app picks the files up on the next load.
• Native pickers (Chromium only): “Open archive…” (showOpenFilePicker), “Extract to folder…” writes entries into a real directory (showDirectoryPicker), and each download row offers “Save as…” (showSaveFilePicker).
• Everywhere else (Firefox, Safari, …) these entry points stay hidden and nothing changes.

How publishing works

.github/workflows/publish.yml runs every Monday 04:00 UTC (and on demand):

1. Resolves the latest upstream tag of ip7z/7zip (or builds a ref you specify via workflow_dispatch)
2. Compiles 7zz to wasm with emscripten (emsdk 4.0.10), single-threaded (ST_MODE=1 — GitHub Pages cannot serve the COOP/COEP headers that SharedArrayBuffer/pthreads would require)
3. Smoke-tests the artifact under Node (create → list → extract → byte-compare)
4. Generates sw-manifest.js (asset list + cache version) and deploys to GitHub Pages

workflow_dispatch with skip_build: true redeploys the site using the wasm from the most recent successful run (useful for shipping UI fixes without a 20-minute rebuild).

Repository layout

Path	Purpose
index.html, app.js	UI (no frameworks, no external resources)
worker.js	Web Worker hosting the wasm engine (callMain per operation)
sw.js, offline.html, manifest.webmanifest	PWA / offline layer
.github/workflows/publish.yml	Weekly build & publish pipeline
.github/scripts/emscripten_shim.c	sysinfo() + umask() shims (see below)
.github/scripts/wasm-smoke-test.mjs	Node roundtrip test run in CI
.github/scripts/generate-sw-manifest.mjs	Writes the versioned precache manifest
icons/	PWA icons
wasm/	Build output — gitignored; CI generates it, drop local builds here for dev

Local development

# put a wasm build in place (CI artifact, or build locally with emsdk), then:
python3 -m http.server -d . 8080
# open http://localhost:8080

Build notes (why the flags are what they are)

• No --no-entry: it removes the main export and emscripten then dead-strips callMain from the glue, even when listed in -sEXPORTED_RUNTIME_METHODS. -sINVOKE_RUN=0 prevents auto-running main instead.
• -sEXIT_RUNTIME=0: callMain may be invoked repeatedly (one call per user operation); EXIT_RUNTIME=1 would tear the runtime down after the first one.
• emscripten_shim.c: emscripten lacks sysinfo() (used by 7-Zip's GetRamSize()), and its __syscall_umask stub starts the process umask at 0777, which would zero 7-Zip's C_umask mask and make every extracted file mode 0000 (EACCES). The shim provides sysinfo() and a POSIX umask() defaulting to 0022.

License / attribution

7-Zip is Copyright (c) 1999-2026 Igor Pavlov, distributed under the GNU LGPL. This repository contains only the web wrapper, CI pipeline and PWA assets; the 7-Zip source is fetched from upstream at build time.