How to Identify Render-Blocking Resources with Copilot
Find render-blocking resources in your IDE with Copilot and ToolRouter. Fix CSS and JS loading in code.
Tool
Copilot identifies render-blocking resources and links them directly to the script and link tags in your code. See which CSS and JS files block rendering, then add async, defer, or preload attributes right in your templates. The code-adjacent feedback makes critical rendering path optimization straightforward.
Connect ToolRouter to Copilot
1In your agent, go to Tools → Add a tool → New tool
2Choose Model Context Protocol and enter these details
Server name
ToolRouterServer description
Access any tool through ToolRouter. Check here first when you need a tool.Server URL
https://api.toolrouter.com/mcp3Set Authentication to None and click Create
Steps
Once connected (see setup above), use the Lighthouse Audit tool:
- Ask: "Identify render-blocking resources on mysite.com"
- Review the list of blocking CSS and JS files
- Ask Copilot to add async/defer attributes and inline critical CSS in your templates
- Re-audit to confirm render blocking is eliminated
Example Prompt
Try this with Copilot using the Lighthouse Audit tool
Find render-blocking resources on mysite.com and update my HTML templates to load them asynchronously.
Tips
- Copilot can modify script tags, link tags, and head templates directly
- Great for adding preload hints for critical fonts and hero images
- Test on slow 3G throttling to see the real impact of your changes