whatsapp — a WhatsApp Client for Linux in C and GTK4

There is a better one now. whatsapp-desktop is the successor to the client described here, built on Electron and Chromium (repository). It does everything below and adds what WebKitGTK could not give this one: voice and video calls with screen sharing, and notifications read from WhatsApp Web's own store rather than inferred from its chat list — so reading a message on your phone takes its notification down at once, a deleted message takes its own with it, and a mention gets through a muted group without letting the rest of the group through behind it.

Everything below is still true, and this client is still maintained. It is 120 KB against 245 MB, and the two install side by side. If that trade is the one you want, read on.

WhatsApp has no Linux client. What we have instead are wrappers: a window with a browser engine inside it, pointed at web.whatsapp.com. That is a perfectly reasonable design — it is the same client WhatsApp serves to Chrome, so nothing about it can get your account banned.

whatsapp is mine. The binary is about 120 KB, written in C against GTK4 and WebKitGTK 6 — and at this size the language is not what decides memory use, the browser engine is. A Python wrapper would have cost perhaps 40 MB more; the engine costs far more than that. C bought a couple of per cent. The real saving came from the cache model, which is further down.

What it is

• WhatsApp Web in a window of its own, with no browser UI around it.
• In the tray, speaking StatusNotifierItem over D-Bus. Closing the window keeps the client connected, and it can start hidden at login.
• In your desktop's font and its dark or light theme, both followed live.
• One notification per message, with the sender, the text and the sender's picture, and a click that opens that conversation.
• An unread badge on the dock icon, and pasted screenshots that actually arrive.

What it is built on

GTK4 for the window, WebKitGTK 6 for the page, and nothing else:

src/main.c     2138 lines — the window, the view, the session, notifications
src/tray.c      421 lines — StatusNotifierItem, spoken directly over D-Bus
src/inject.js   877 lines — what runs inside WhatsApp's own page

inject.js is turned into a header at build time and compiled in, so the client is still one binary with nothing beside it. There is no libayatana-appindicator, no notification library and no JavaScript framework: the dependencies are the two libraries above and the GLib that comes with them.

The tray, without a tray library

GTK4 removed GtkStatusIcon, and the usual replacement is packaged only for GTK2 and GTK3 — neither of which can be linked into a GTK4 process.

Underneath all of those wrappers is a D-Bus protocol, StatusNotifierItem, and GNOME already runs a watcher for it. Speaking it directly costs one file and no dependencies, and it hands you the parts a wrapper usually hides. The unread count comes from WhatsApp's own document title, which becomes (3) WhatsApp when chats are waiting, and that same number goes out again as a com.canonical.Unity.LauncherEntry signal — which is what puts the badge on the dock icon.

The cache model, which is where the memory went

The client that sent me down this road sat at 1.8 GB. Two things were behind it, and neither was the one everybody assumes.

On disk, serviceworkers/Scripts held 1.4 GB — 267 copies of the same file, about 5.3 MB each, six months' worth. WhatsApp Web ships a new service-worker build every day or two and WebKitGTK never evicts the superseded ones. Nothing reaps them. This client reaps them at startup, and the cache settles at about 5 MB.

In memory, the answer was not a smaller ceiling. Capping WebKit's cache makes it worse: the page re-fetches and re-decodes what it just threw away, and you pay for the same bytes twice. What works is a memory-pressure handler that lets the cache stay large while there is room and releases it when the system actually asks — so the client is generous when the machine is idle and gets out of the way when it is not.

Emoji that survive a restart

WhatsApp Web does not draw emoji with a font. It draws them from 152 sprite sheets of about 30 KB each and picks which set to fetch from your display resolution — and WebKit's disk cache kept not one of them, so every launch pulled 4.7 MB down again and the emoji panel sat full of blank squares for half a minute.

Warming them on startup is the obvious fix and it is the wrong one: WhatsApp preloads every sheet itself with an XHR, so a warm-up races that preload for the same bytes over the same connections and both halves arrive slower. This client caches the sheets to disk itself instead, keyed by URL, and serves them back on the next launch. The panel is filled before you can open it.

The page fixes

Three small things run inside WhatsApp's own page, each because the engine underneath needed them:

• The clipboard. WebKitGTK handed the page an empty clipboardData for images, so a real Ctrl+V arrived with nothing in it. The bytes are lifted off the GTK clipboard and dispatched into the page by hand.
• The user agent. WebKit's default identifies as Safari on a Mac, and WhatsApp offers you the Mac app forever. It is replaced with one WhatsApp reads as a Linux desktop browser.
• Arabic. WhatsApp's line boxes do not leave room for the descenders Arabic needs, and the bowl of a final ن or ي gets shorn off. The fix is a wider clip, never a taller line — line-height moves every Arabic line off the rhythm the page was designed on, and inside the composer a line one pixel too tall makes the box scrollable, which makes the browser scroll the caret back into view on every keystroke.

Installing it

From the shinux repository:

sudo dnf install whatsapp     # Fedora and friends
sudo apt install whatsapp     # Debian, Ubuntu 24.04+
sudo pacman -S whatsapp       # Arch, with the repo added

If you have not added the repository yet:

curl -fsSL https://abdallah-shehawey.github.io/shinux-repo/install.sh | sudo sh

Packages are also attached to every GitHub release — RPM, DEB and a native Arch package.

The source

github.com/abdallah-shehawey/whatsapp, GPL-3.0. The Chromium client that grew out of it is whatsapp-desktop.