diff --git a/src/lib/filter-entries.test.ts b/src/lib/filter-entries.test.ts
index 78ffafc..8de45af 100644
--- a/src/lib/filter-entries.test.ts
+++ b/src/lib/filter-entries.test.ts
@@ -1,5 +1,6 @@
 import { test, expect } from '@playwright/test'
 import { filter_coverage } from './filter-entries.js'
+import { Coverage } from './parse-coverage.js'
 
 test('filters out JS files', () => {
 	let entries = [
@@ -8,7 +9,7 @@ test('filters out JS files', () => {
 			text: 'console.log("Hello world")',
 			ranges: [{ start: 0, end: 25 }],
 		},
-	]
+	] satisfies Coverage[]
 	expect(filter_coverage(entries)).toEqual([])
 })
 
@@ -19,7 +20,7 @@ test('keeps files with CSS extension', () => {
 			text: 'a{color:red}',
 			ranges: [{ start: 0, end: 13 }],
 		},
-	]
+	] satisfies Coverage[]
 	expect(filter_coverage(entries)).toEqual(entries)
 })
 
@@ -37,7 +38,7 @@ test('keeps extension-less URL with HTML text', () => {
 			text: 'a{color:red;}',
 			ranges: [{ start: 0, end: 13 }], // ranges are remapped
 		},
-	]
+	] satisfies Coverage[]
 	expect(filter_coverage(entries)).toEqual(expected)
 })
 
@@ -48,6 +49,17 @@ test('keeps extension-less URL with CSS text (running coverage in vite dev mode)
 			text: 'a{color:red;}',
 			ranges: [{ start: 0, end: 13 }],
 		},
-	]
+	] satisfies Coverage[]
 	expect(filter_coverage(entries)).toEqual(entries)
 })
+
+test('filters out extension-less JS', () => {
+	let entries = [
+		{
+			url: 'http://example.com',
+			text: 'var a = 10; console.log(a);',
+			ranges: [{ start: 0, end: 29 }],
+		},
+	] satisfies Coverage[]
+	expect(filter_coverage(entries)).toEqual([])
+})
diff --git a/src/lib/filter-entries.ts b/src/lib/filter-entries.ts
index ca9ea82..2b3d63c 100644
--- a/src/lib/filter-entries.ts
+++ b/src/lib/filter-entries.ts
@@ -6,6 +6,26 @@ function is_html(text: string): boolean {
 	return /<\/?(html|body|head|div|span|script|style)/i.test(text)
 }
 
+// Matches: element selectors, class/id selectors, attribute selectors, @rules
+const SELECTOR_REGEX = /(@[a-z-]+|\[[^\]]+\]|[a-zA-Z_#.-][a-zA-Z0-9_-]*)\s*\{/
+// Check for CSS properties (property: value pattern)
+const DECLARATION_REGEX = /^\s*[a-zA-Z-]+\s*:\s*.+;?\s*$/m
+
+function is_css_like(text: string): boolean {
+	return SELECTOR_REGEX.test(text) || DECLARATION_REGEX.test(text)
+}
+
+function is_js_like(text: string): boolean {
+	try {
+		// Only parses the input, does not execute it.
+		// NEVER EXECUTE THIS UNTRUSTED CODE!!!
+		new Function(text)
+		return true
+	} catch {
+		return false
+	}
+}
+
 export function filter_coverage(coverage: Coverage[]): Coverage[] {
 	let result = []
 
@@ -29,13 +49,13 @@ export function filter_coverage(coverage: Coverage[]): Coverage[] {
 			continue
 		}
 
-		// At this point it can only be CSS
-		// TODO: that's not true, check if it's css-like of js-like
-		result.push({
-			url: entry.url,
-			text: entry.text,
-			ranges: entry.ranges,
-		})
+		if (is_css_like(entry.text) && !is_js_like(entry.text)) {
+			result.push({
+				url: entry.url,
+				text: entry.text,
+				ranges: entry.ranges,
+			})
+		}
 	}
 
 	return result
diff --git a/src/lib/html-parser.test.ts b/src/lib/html-parser.test.ts
index bd04d9b..297b773 100644
--- a/src/lib/html-parser.test.ts
+++ b/src/lib/html-parser.test.ts
@@ -36,10 +36,16 @@ test('finds style tags with attributes', () => {
 	expect(parse('<style data-attr data-testid="yup">.css{}</style>')).toEqual([{ textContent: '.css{}' }])
 })
 
-test('ignores style tags without end tag', () => {
-	expect(parse('<style>.css{}')).toEqual([])
-})
-
-test('ignores style tags without closing opening tag', () => {
-	expect(parse('<style .css{}')).toEqual([])
+test.describe('invalid tags', () => {
+	test('ignores style tags without end tag', () => {
+		expect(parse('<style>.css{}')).toEqual([])
+	})
+
+	test('ignores style tags without closing opening tag', () => {
+		expect(parse('<style .css{}')).toEqual([])
+	})
+
+	test('custom element: <style-thing>', () => {
+		expect(parse('<style-thing>.css{}</style-thing>')).toEqual([])
+	})
 })