diff --git a/css_filter_test.go b/css_filter_test.go
index 1cfe066..7d7ad5d 100644
--- a/css_filter_test.go
+++ b/css_filter_test.go
@@ -1,6 +1,8 @@
 package main
 
 import (
+	"fmt"
+	"strings"
 	"testing"
 )
 
@@ -166,3 +168,44 @@ func TestFilterSelectorsAgainstHTML(t *testing.T) {
 		}
 	}
 }
+
+func TestBuildElementHidingCSSChunking(t *testing.T) {
+	// Build a selector list larger than maxSelectorsPerRule
+	n := maxSelectorsPerRule + 500
+	selectors := make([]string, n)
+	for i := range selectors {
+		selectors[i] = fmt.Sprintf(".sel-%d", i)
+	}
+
+	css := buildElementHidingCSS(selectors)
+
+	// Should produce 2 rules
+	count := strings.Count(css, "display: none !important")
+	if count != 2 {
+		t.Errorf("expected 2 CSS rules, got %d", count)
+	}
+
+	// First selector and last selector should both be present
+	if !strings.Contains(css, ".sel-0") {
+		t.Error("first selector missing")
+	}
+	if !strings.Contains(css, fmt.Sprintf(".sel-%d", n-1)) {
+		t.Error("last selector missing")
+	}
+}
+
+func TestBuildElementHidingCSSSmallList(t *testing.T) {
+	css := buildElementHidingCSS([]string{".a", ".b", ".c"})
+
+	count := strings.Count(css, "display: none !important")
+	if count != 1 {
+		t.Errorf("expected 1 CSS rule for small list, got %d", count)
+	}
+}
+
+func TestBuildElementHidingCSSEmpty(t *testing.T) {
+	css := buildElementHidingCSS(nil)
+	if css != "" {
+		t.Errorf("expected empty string for nil selectors, got %q", css)
+	}
+}
diff --git a/elemhide_inject.go b/elemhide_inject.go
index 5252959..6b1bb27 100644
--- a/elemhide_inject.go
+++ b/elemhide_inject.go
@@ -223,13 +223,31 @@ func mergeElementHidingSelectors(baseline, user *blocklist.ElementHiding, userRS
 	return selectors
 }
 
+// maxSelectorsPerRule limits the number of selectors in a single CSS rule.
+// Chrome truncates rules that exceed its internal selector limit (~4096),
+// silently breaking element hiding. Chunking into multiple rules avoids this.
+const maxSelectorsPerRule = 4096
+
 // buildElementHidingCSS produces a display:none stylesheet from a list of
-// CSS selectors. Returns empty string if the list is empty.
+// CSS selectors. Rules are chunked to stay within browser selector limits.
+// Returns empty string if the list is empty.
 func buildElementHidingCSS(selectors []string) string {
 	if len(selectors) == 0 {
 		return ""
 	}
-	return strings.Join(selectors, ",\n") + " {\n  display: none !important;\n}\n"
+	if len(selectors) <= maxSelectorsPerRule {
+		return strings.Join(selectors, ",\n") + " {\n  display: none !important;\n}\n"
+	}
+	var b strings.Builder
+	for i := 0; i < len(selectors); i += maxSelectorsPerRule {
+		end := i + maxSelectorsPerRule
+		if end > len(selectors) {
+			end = len(selectors)
+		}
+		b.WriteString(strings.Join(selectors[i:end], ",\n"))
+		b.WriteString(" {\n  display: none !important;\n}\n")
+	}
+	return b.String()
 }
 
 // injectBeforeClose inserts content before the first found closing tag,