URL: /rules/perf --- title: "Performance" description: "Page speed and loading performance" --- Page speed and loading performance ## Rules Checks for large GIFs that could be converted to video Lists performance audits that require browser execution Checks Cache-Control header configuration Checks for Cumulative Layout Shift prevention Checks for Gzip or Brotli compression Identifies chains of dependent resources that delay rendering Checks for CSS files that exceed recommended size limits Checks for JavaScript files that exceed recommended size limits Detects excessive DOM complexity that impacts performance Detects duplicate JavaScript libraries loaded multiple times Checks for font loading best practices Checks for HTTP/2 protocol support Checks for Interaction to Next Paint optimization Detects JavaScript resources that return 3XX redirects Detects JavaScript libraries and checks for known vulnerabilities Detects lazy loading on likely above-fold images Checks for Largest Contentful Paint optimization opportunities Detects ES5 polyfills and legacy JavaScript code Checks for preconnect hints to critical third-party origins Checks for render-blocking CSS and JavaScript Checks for source map availability and configuration Measures server response time (TTFB) Checks the total byte weight of the page Detects unminified CSS that could be optimized Detects unminified JavaScript that could be optimized ## Disable All Performance Rules ```toml squirrel.toml [rules] disable = ["perf/*"] ```