diff --git a/fix_css.mjs b/fix_css.mjs
new file mode 100644
index 000000000..e465916c2
--- /dev/null
+++ b/fix_css.mjs
@@ -0,0 +1,141 @@
+import { readFile, writeFile, readdir as readDir, rm } from "node:fs/promises";
+import { parse, latestEcmaVersion } from "espree";
+import { traverse, Syntax } from "estraverse";
+import { resolve as pathResolve, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const classRegex = /(\.[a-zA-Z0-9_-]+)/g;
+
+const paths = [
+	"./Scripts/WebUI/",
+	"./ClientExtracted/",
+	"./help.steampowered.com/",
+	"./partner.steamgames.com/",
+	"./steamcommunity.com/",
+	"./store.steampowered.com/",
+	"./www.dota2.com/",
+	"./www.underlords.com/",
+	"./www.counter-strike.net/",
+];
+
+async function ParseJsFile(file, classNames) {
+	if (file.endsWith("licenses.js")) {
+		return;
+	}
+
+	try {
+		const code = await readFile(file);
+		const ast = parse(code, {
+			ecmaVersion: latestEcmaVersion,
+			sourceType: "module",
+			loc: true,
+		});
+
+		traverse(ast, {
+			enter: (node) => {
+				// console.log(node);
+				if (
+					node.type === Syntax.AssignmentExpression &&
+					node.left.type === Syntax.MemberExpression &&
+					node.left.property.type === Syntax.Identifier &&
+					node.left.property.name === "exports" &&
+					node.right.type === Syntax.ObjectExpression &&
+					node.right.properties.constructor === Array
+				) {
+					for (const array_node of node.right.properties) {
+						if (array_node.value.type !== Syntax.Literal || isNumber(String(array_node.value.value), 2)) {
+							continue;
+						}
+						if (!Object.hasOwn(classNames, array_node.value.value)) {
+							classNames[array_node.value.value] = [array_node.key.name];
+						} else {
+							if (!classNames[array_node.value.value].includes(array_node.key.name)) {
+								classNames[array_node.value.value].push(array_node.key.name);
+							}
+						}
+					}
+				}
+			},
+		});
+	} catch (e) {
+		console.error(`Unable to parse "${file}":`, e);
+	}
+}
+
+async function FixCssFile(path, classNames) {
+	try {
+		const css = (await readFile(path)).toString();
+		let output = css;
+		const matches = [...new Set(css.match(classRegex))];
+		if (matches) {
+			for (const match of matches) {
+				if (Object.hasOwn(classNames, match.slice(1))) {
+					// replacing by multiple classes creates non valid css but it makes it easy to detect issues
+					output = output.replaceAll(match, `.${classNames[match.slice(1)].join("|")}`);
+				}
+			}
+		}
+		const outputPath = path.replace(".css", ".fixed.css");
+		if (output !== css) {
+			await writeFile(outputPath, output);
+		} else {
+			// best effort to clean our mess if we did some,
+			// although it might have some problematic effect if the Js parse part need a fix at some point in time
+			await rm(outputPath, { force: true });
+		}
+	} catch (e) {
+		console.error(`Unable to fix "${path}":`, e);
+	}
+}
+
+async function* GetRecursiveFiles(dir, ext) {
+	const dirents = await readDir(dir, { withFileTypes: true });
+	for (const dirent of dirents) {
+		const res = pathResolve(dir, dirent.name);
+		if (dirent.isDirectory()) {
+			yield* GetRecursiveFiles(res, ext);
+		} else if (dirent.isFile() && dirent.name.endsWith(ext)) {
+			yield res;
+		}
+	}
+}
+
+// Why is this not working?
+// function isNumber(string, nbrRecursiceSlice = 0) {
+//     return !Number.isNaN(Number(string)) || (string.length > 0 && nbrRecursiceSlice > 0 ) ? isNumber(string.slice(0,-1), nbrRecursiceSlice - 1) :  false;
+// }
+
+// best effort to guess if a string is a number (tries to remove the unit at the end)
+function isNumber(string, nbrRecursiceSlice) {
+	while (string.length > 0 && nbrRecursiceSlice > 0) {
+		if (Number.isNaN(Number(string))) {
+			string = string.slice(0, -1);
+		} else {
+			return true;
+		}
+	}
+	return false;
+}
+
+if (process.argv.length > 2) {
+	const classNames = {};
+	const __dirname = dirname(fileURLToPath(import.meta.url));
+	const jsPath = process.argv[2].replace(__dirname, "").split("/")[1];
+
+	for await (const file of GetRecursiveFiles(jsPath, ".js")) {
+		await ParseJsFile(file, classNames);
+	}
+	await FixCssFile(process.argv[2], classNames);
+} else {
+	for (const path of paths) {
+		const classNames = {};
+
+		for await (const file of GetRecursiveFiles(path, ".js")) {
+			await ParseJsFile(file, classNames);
+		}
+
+		for await (const file of GetRecursiveFiles(path, ".css")) {
+			await FixCssFile(file, classNames);
+		}
+	}
+}
diff --git a/update.php b/update.php
index 284fa94cb..aa2274cd2 100644
--- a/update.php
+++ b/update.php
@@ -587,6 +587,11 @@ private function HandleResponse( string $File, string $Data, string $URL ) : boo
 
 				system( 'npm run prettier ' . escapeshellarg( $File ) );
 
+				if( str_ends_with( $File, '.css' ) )
+				{
+					system( 'node fix_css.mjs ' . escapeshellarg( $File ) );
+				}
+
 				return true;
 			}
 
@@ -940,6 +945,15 @@ private function ProcessManifests( array $KnownUrls ) : array
 						$this->Log( 'Chunk ' . $FilepathOnDisk . ' no longer exists in manifest' );
 
 						unlink( $FilepathOnDisk );
+
+						if ( str_ends_with( $Filename, '.css'))
+						{
+							$FixedFilepathOnDisk = str_replace('.css', '.fixed.css', $FilepathOnDisk);
+							if ( file_exists( $FixedFilepathOnDisk) ){
+								unlink( $FixedFilepathOnDisk );
+							}
+							
+						}
 					}
 				}
 			}