Third-party scripts are the #1 cause of slow websites—unoptimized loading can add 2-5 seconds to your page load time.
Quick Reference
- Use async for independent scripts (analytics, ads)
- Use defer for DOM-dependent scripts (chat widgets, social)
- Lazy-load non-critical scripts after page load
- Consider self-hosting critical third-party scripts
Check
Analyze third-party scripts on this page to ensure they use async/defer and don't block rendering.
Fix
Add async or defer attributes to third-party scripts and consider lazy loading non-critical scripts.
Explain
Explain the performance impact of third-party scripts and strategies to minimize their blocking effect.
Code Review
Review the routes, assets, and loading behavior that affect Optimize third-party script loading. Flag exact files, requests, or rendering steps that add unnecessary network, CPU, or layout cost, and describe the measurement method used to confirm the issue.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/performance/third-party-scripts