KoboPatch Web UI

A web application that provides a GUI for applying custom kobopatch patches to Kobo e-readers. It uses the File System Access API (Chromium) to interface with connected Kobo devices, or falls back to manual model/firmware selection on other browsers.

The app makes it easy to configure which patches to apply, downloads the correct firmware from Kobo's servers, runs the patcher (compiled to WebAssembly), and places the resulting KoboRoot.tgz on the device. The user then reboots to apply.

Fully client-side — no backend needed, can be hosted as a static site. Patches are community-contributed via MobileRead and need to be manually updated when new Kobo firmware versions come out.

User flow

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

Add the patch zip to src/public/patches/ and update index.json
Add firmware download URLs to FIRMWARE_DOWNLOADS in kobo-device.js (keyed by version then serial prefix)
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.

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