Google Confirms: CSS Class Names Don’t Influence SEO

There’s an SEO myth that naming your CSS classes after your target keywords will give your pages a rankings boost. At O’Brien Media, we believe in separating fact from fiction—so when Google’s own Martin Splitt and John Mueller addressed this in the latest Search Off the Record podcast, we took notice.

Class Names: Harmless Styling, No Ranking Power

During the episode, Splitt was unequivocal:

“CSS class names are just assigning stylesheet rules to elements. You could name them all ‘blurb’—it wouldn’t change your SEO.”
—Martin Splitt

Mueller added that class attributes are stripped out when Googlebot crawls your pages—they’re never treated as content or keywords. In other words, your class names are for your developers, not for search engines.

Pseudo‑Elements: Decorative Only

You might be tempted to insert “NEW!” or a hashtag before product titles with ::before or ::after. Splitt reminded us that pseudo‑elements are purely presentational; anything inserted with CSS pseudo‑selectors does not appear in the DOM and is invisible to Googlebot—and to screen readers too. If that text matters for SEO or accessibility, it needs to live in your HTML markup.

When CSS Does Matter: File Size & Performance

While class names themselves don’t influence rankings, the size of your CSS files can. According to the HTTP Archive’s 2022 Web Almanac, the median stylesheet weighed around 68 KB on mobile and 72 KB on desktop. Splitt noted examples of bloated CSS files—one topped 78 MB—delaying render times and affecting Core Web Vitals.

Fast, lean CSS is a technical SEO win: minify, purge unused rules, and split large files into critical and non‑critical bundles so that your pages load and render quickly.

Keep Your CSS Crawlable

Google’s guidelines recommend making your CSS files crawlable so that pages render just as users see them. If you block stylesheets via robots.txt or HTTP headers, you risk:

• Incorrect mobile‑friendliness assessments
• Rendering mismatches that hide real content
• Misleading layout interpretations by Googlebot

For reference, see Google’s Robots.txt guide on when—and when not—to block resource files.

Practical Takeaways for Your Site

1. Stop keyword‑doping class names. Focus on semantic HTML for your content hierarchy; leave styling hooks to CSS.
2. Audit pseudo‑elements. Ensure no meaningful text is hidden behind ::before or ::after.
3. Trim your styles. Use tools like PurgeCSS and PostCSS to remove unused rules and split critical CSS.
4. Verify crawlability. Check your robots.txt and HTTP headers so that Googlebot can fetch your stylesheets and render your pages accurately.
5. Monitor performance. Keep an eye on Core Web Vitals—large or blocked CSS files can hurt LCP and FID metrics.

Need a Hand?

At O’Brien Media, we help small businesses keep their technical SEO sharp—from lean CSS strategies to full website audits. If you’d like support optimizing your stylesheets, ensuring proper rendering, or auditing your site’s performance, get in touch today.