Google has confirmed that CSS class names have no influence on how its search engine indexes or ranks pages. The clarification comes from the latest podcast episode of "Search Off the Record," recorded at the company’s Mountain View headquarters.
CSS class names and SEO
Developer Advocate Martin Splitt explained that class names are examined only for styling. Search Advocate John Mueller added that Googlebot does not treat them as keywords or ranking factors.
- CSS class names carry zero ranking weight.
- Content injected with
:beforeor:afterpseudo elements is ignored because it never reaches the rendered DOM Google analyzes. - Blocking Google from fetching CSS files can break rendering and hurt indexing.
CSS and page rendering
Splitt urged developers to keep all meaningful text in the HTML source, not in pseudo elements. Mueller cited a real case where hashtag icons inserted with :before were invisible to Google’s crawler, leading to lost context in search results.
The team also warned about oversized stylesheets. According to the HTTP Archive’s 2022 Web Almanac, the median mobile CSS file is 68 KB, while the largest recorded file topped 78 MB. Excessive file size slows loading and can hurt Core Web Vitals, which feed into Google’s user-experience ranking signals.
Recommended mitigations include minification, removing unused rules, and testing performance with PageSpeed Insights.
Background
Google began asking site owners to keep CSS crawlable in 2014, when it shifted toward rendering pages as modern browsers do. Core Web Vitals were folded into the ranking system in 2021, further tying file size and load speed to organic visibility. Since its 2020 launch, the "Search Off the Record" podcast has served as a venue for debunking technical SEO myths.
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