A menu-bar app dropped 274 MB by rendering on the webview macOS already ships

Start with the arithmetic, because the title's 15 MB is not a figure the post prints. It reports the packaged app as 18.9x smaller and a 94.7% reduction in what a user downloads ^[13]. 289 divided by 18.9 is 15.29 ^[21]. 289 less 94.7% is 15.32 ^[22]. The two ratios agree, and 15 MB is rounded down from about 15.3.

Both ends of that ratio come from one command. `du -sh dist/mac-arm64/WatchMe.app` reported 289M ^[3]. "289 MB. To list processes and show a notification," the developer wrote ^[28]. du measures the uncompressed bundle on an arm64 disk, and a user downloads a compressed archive, for which the post gives no number ^[27].

The saving has a single source. Electron shipped an entire Chromium build so that a table could be rendered, and macOS already has a webview that every other app uses for free ^[5]. "Tauri doesn't make your app fast. It makes your app small, by not shipping a browser," the developer wrote ^[6]. No timing or memory measurement appears in the post in either direction ^[27].

So the transfer condition is about layout, not about OS access. WatchMe's interface is a table and two checkboxes, sitting on top of three operations that touch the OS: enumerate processes, own a tray icon, post a notification ^[4]. Nothing there depends on a particular rendering engine. An app that pins a Chromium version to get its layout right is buying something with that 274 MB ^[23].

The IPC delta is the part worth copying regardless. The Electron version needed three artifacts: an `ipc-channels.json` listing five channel names, a `preload.js` re-exposing each one through `contextBridge`, and `ipcMain.handle` registrations in the main process ^[7]. Tauri needs one attribute. `#[tauri::command] fn get_processes()` on the Rust side, `invoke('get_processes')` in the renderer, and the channel name is the function name ^[8]. The npm dependency went with it: `sysinfo` enumerates processes in the Rust core, and the renderer still reads the same `pid`, `name` and `cmd` ^[9][10].

The bundle shrank and the repository grew. That single commit was +12,154 and -4,875, a net gain of 7,279 lines ^[14][24]. Around 220 lines of Electron main-process JavaScript became Rust ^[16]. Another 579 lines of scaffolding for booting and driving a packaged Electron app were deleted, roughly 11.9% of the deletions in the commit ^[11][25]. The harness did not go away because Tauri replaced it: "The logic worth testing was always plain JavaScript; it just hadn't been separated from Electron," the developer wrote ^[12].

Claude Code did most of the typing ^[15]. The port suited that: known shape, documented target API, and "Rust's type checker is a brutal reviewer, and having one is what makes AI-written Rust tolerable" ^[17]. The find the developer rates highest came after the port. While rebuilding the UI, the model read the renderer and flagged `row.classList.add('highlighted-row')`, a class added on 19 September 2024 and never defined in any stylesheet ^[18][20]. For 721 days, close to two years, the only sign that a process was being watched was the checkbox the user had just ticked ^[19][26].