Find your Slack's application directory.
Windows: %homepath%\AppData\Local\slack\
Mac: /Applications/Slack.app/Contents/
Linux: /usr/lib/slack/ (Debian-based)
Open up the most recent version (e.g. app-2.5.1) then open resources\app.asar.unpacked\src\static\index.js
For versions after and including 3.0.0 the same code must be added to the following file resources\app.asar.unpacked\src\static\ssb-interop.js
At the very bottom, add
// First make sure the wrapper app is loaded
document.addEventListener("DOMContentLoaded", function() {
// Then get its webviews
let webviews = document.querySelectorAll(".TeamView webview");
// Fetch our CSS in parallel ahead of time
const cssPath = 'https://raw.githubusercontent.com/C0axx/slack/master/black.css';
let cssPromise = fetch(cssPath).then(response => response.text());
let customCustomCSS = `
:root {
/* Modify these to change your theme colors: */
--primary: #09F;
--text: #CCC;
--background: #080808;
--background-elevated: #222;
}
`
// Insert a style tag into the wrapper view
cssPromise.then(css => {
let s = document.createElement('style');
s.type = 'text/css';
s.innerHTML = css + customCustomCSS;
document.head.appendChild(s);
});
// Wait for each webview to load
webviews.forEach(webview => {
webview.addEventListener('ipc-message', message => {
if (message.channel == 'didFinishLoading')
// Finally add the CSS into the webview
cssPromise.then(css => {
let script = `
let s = document.createElement('style');
s.type = 'text/css';
s.id = 'slack-custom-css';
s.innerHTML = \`${css + customCustomCSS}\`;
document.head.appendChild(s);
`
webview.executeJavaScript(script);
})
});
});
});
#080808,#080808,#080808,#8BE9FD,#6272A4,#FFFFFF,#50FA7B,#FF5555