# Render-blocking resources
Category: [Rendering & JavaScript](https://seo-geo-glossary.com/en/glossary/category/rendering-javascript/) › [How search engines render](https://seo-geo-glossary.com/en/glossary/category/rendering-javascript/how-search-engines-render/)
**Render-blocking resources** are files, mostly CSS and JavaScript, that the browser has to load and process before it can display page content. MDN notes that render-blocking increases the time until users can see content or interact. Resources blocked by robots.txt are a separate topic.
## What does Lighthouse flag?
Lighthouse flags two kinds of URLs as render-blocking:
- a `
```
The script downloads without stopping the HTML parser. The print stylesheet does not hold back the screen display.
## Related terms
- [Blocked resources](https://seo-geo-glossary.com/en/glossary/blocked-resources/index.md)
- [Total Blocking Time (TBT)](https://seo-geo-glossary.com/en/glossary/total-blocking-time/index.md)
- [Largest Contentful Paint (LCP)](https://seo-geo-glossary.com/en/glossary/largest-contentful-paint/index.md)
- [First Contentful Paint (FCP)](https://seo-geo-glossary.com/en/glossary/first-contentful-paint/index.md)
- [Core Web Vitals](https://seo-geo-glossary.com/en/glossary/core-web-vitals/index.md)
- [Critical CSS](https://seo-geo-glossary.com/en/glossary/critical-css/index.md)
- [Page speed](https://seo-geo-glossary.com/en/glossary/page-speed/index.md)
## Sources
- [Render-blocking – MDN Glossary](https://developer.mozilla.org/en-US/docs/Glossary/Render_blocking)
- [Eliminate render-blocking resources – Lighthouse (Chrome for Developers)](https://developer.chrome.com/docs/lighthouse/performance/render-blocking-resources)
- [Optimize resource loading – web.dev](https://web.dev/learn/performance/optimize-resource-loading)
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Last updated: October 7, 2026
URL: https://seo-geo-glossary.com/en/glossary/render-blocking-resources/