KoboPatch Web UI

Fully client-side web app for applying kobopatch patches to Kobo e-readers. No backend — runs entirely in the browser via WebAssembly. Can be hosted as a static site.

User flow

1. Select device (auto-detect via File System Access API on Chromium, or manual dropdowns on any browser)
2. Configure patches (enable/disable, PatchGroup mutual exclusion via radio buttons)
3. Build — firmware auto-downloaded from Kobo's CDN (ereaderfiles.kobo.com, CORS open), patched via WASM in a Web Worker
4. Write KoboRoot.tgz to device (Chromium auto mode) or download manually

File structure

src/public/                     # Webroot — serve this directory
  index.html                    # Single-page app, 3-step wizard (Device → Patches → Build)
  style.css
  app.js                        # Step navigation, flow orchestration, firmware download with progress
  kobo-device.js                # KOBO_MODELS (serial prefix → name), FIRMWARE_DOWNLOADS (version+prefix → URL),
                                #   getDevicesForVersion(), getFirmwareURL(), KoboDevice class (File System Access API)
  patch-ui.js                   # PatchUI class: loads patch zips (JSZip), parses YAML, renders toggle UI,
                                #   generates kobopatch.yaml config with overrides
  kobopatch.js                  # KobopatchRunner: spawns Web Worker per build, handles progress/done/error messages
  patch-worker.js               # Web Worker: loads wasm_exec.js + kobopatch.wasm, runs patchFirmware(),
                                #   posts progress back, transfers result buffer zero-copy
  wasm_exec.js                  # Go WASM support runtime (copied from Go SDK by setup.sh, gitignored)
  kobopatch.wasm                # Compiled WASM binary (built by build.sh, gitignored)
  patches/
    index.json                  # [{ "version": "4.45.23646", "filename": "patches_4.45.23646.zip" }]
    patches_*.zip               # Each contains kobopatch.yaml + src/*.yaml patch files

kobopatch-wasm/                 # WASM build
  main.go                       # Go entry point: jsPatchFirmware() → patchFirmware() pipeline
                                #   Accepts configYAML, firmwareZip, patchFiles, optional progressFn
                                #   Returns { tgz: Uint8Array, log: string }
  go.mod
  setup.sh                      # Clones kobopatch source, copies wasm_exec.js
  build.sh                      # GOOS=js GOARCH=wasm go build, copies .wasm to src/public/,
                                #   sets ?ts= cache-bust timestamp in patch-worker.js

Adding a new firmware version

1. Add the patch zip to src/public/patches/ and update index.json
2. Add firmware download URLs to FIRMWARE_DOWNLOADS in kobo-device.js (keyed by version then serial prefix)
3. The kobo CDN prefix per device family (e.g. kobo12, kobo13) is stable; the date path segment changes per release

Building the WASM binary

Requires Go 1.21+.

cd kobopatch-wasm
./setup.sh    # first time only
./build.sh    # compiles WASM, copies to src/public/

Running locally

python3 -m http.server -d src/public/ 8888

Credits

kobopatch by pgaskin. Patches from MobileRead.