Explore

Use when auditing slow page loads, heavy assets, or rendering delays related to Reduce DOM size and complexity. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when reviewing scripts, client components, bundles, or runtime behavior related to Minimize costly DOM read/write operations. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug. In React, repeated requestAnimationFrame-driven state updates across multiple mounted components are a valid performance smell when visible in the source.

Use when reviewing rendered HTML, interactive components, or design-system patterns related to Wrap definition items in a definition list. Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output where relevant.

Use when auditing YMYL content pages for trust signals, generating disclaimer copy for medical or financial content, or reviewing affiliate disclosure requirements under FTC or ASA guidelines.

Use when reviewing templates, rendered HTML, or shared components related to Set text direction for RTL languages. Validate the final browser-facing markup, not just the source framework abstraction.

Use when reviewing image assets, markup, and CDN or build transforms related to Set explicit width and height on images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together. Separate real CLS risks from tiny decorative SVGs or ornament-only assets that are unlikely to move surrounding content.

Use when reviewing rendered HTML, interactive components, or design-system patterns related to Use correct definition list structure. Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output where relevant.

Use when reviewing templates, rendered HTML, or shared components related to Load scripts with defer, async, or type=module. Validate the final browser-facing markup, not just the source framework abstraction.

Use when reviewing rendered HTML, interactive components, or design-system patterns related to Hide decorative elements from assistive technology. Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output where relevant. If an image is clearly decorative, default to no finding unless the snippet shows an actual issue such as broken semantics, focusability, or visible layout instability.

Use when reviewing scripts, client components, bundles, or runtime behavior related to Debounce and throttle event handlers. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.

Use when auditing a site's internal link graph for dead-end pages, suggesting related-content links to add to thin or standalone pages, or reviewing CMS templates that produce link-free content pages.

Use when reviewing form components, API payloads, or client-side storage to identify fields that are collected but not consumed by a stated feature.

Use when reviewing stylesheets, component styles, and responsive behavior related to Support dark mode with prefers-color-scheme. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing custom element class definitions or Web Component source code to check for missing ARIA reflection, keyboard handling, and form association.

Use when reviewing utility functions, component props, or template strings that format numbers, prices, or dates to check whether Intl APIs are used correctly.

Use when auditing slow page loads, heavy assets, or rendering delays related to Minimize cumulative layout shift. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when reviewing stylesheets, component styles, and responsive behavior related to Include a print stylesheet. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing stylesheets, component styles, and responsive behavior related to Order CSS files correctly. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing stylesheets, component styles, and responsive behavior related to Load CSS without blocking render. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing stylesheets, component styles, and responsive behavior related to Minify all CSS files. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing stylesheets, component styles, and responsive behavior related to Use CSS Grid for two-dimensional layouts. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when auditing slow page loads, heavy assets, or rendering delays related to Optimize CSS file size. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when reviewing stylesheets, component styles, and responsive behavior related to Use CSS custom properties for design tokens. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing CI coverage, automated checks, or test strategy related to Test on real mobile devices and viewports. Focus on whether the rule is continuously verified, not just documented.

Use when reviewing image assets, markup, and CDN or build transforms related to Serve images from a CDN. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.

Use when reviewing CI coverage, automated checks, or test strategy related to Implement end-to-end testing. Focus on whether the rule is continuously verified, not just documented.

Use when reviewing a project's security posture, setting up CI pipelines, or responding to a reported vulnerability in a dependency.

Use when reviewing stylesheets, component styles, and responsive behavior related to Inline critical CSS for faster rendering. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when reviewing stylesheets, component styles, and responsive behavior related to Use CSS containment to limit repaint scope. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when implementing animated gradients, complex CSS transitions that involve custom property values, or building a typed design token system where custom property misuse should produce visible errors.

Use when reviewing scripts, client components, bundles, or runtime behavior related to Handle cross-origin requests securely. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.

Use when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation. Check both headers and real browser behavior.

Use when reviewing CI coverage, automated checks, or test strategy related to Test across all major browsers. Focus on whether the rule is continuously verified, not just documented.

Use when auditing slow page loads, heavy assets, or rendering delays related to Minimize critical request chains. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when reviewing image assets, markup, and CDN or build transforms related to Prioritize loading critical images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.

Use when reviewing a website for GDPR/CCPA compliance, specifically whether cookie consent is obtained before non-essential cookies are set.

Use when setting up integration testing for a frontend-backend API boundary, evaluating whether two services are safe to deploy independently, or replacing slow end-to-end tests with contract tests.

Use when reviewing rendered HTML, layout components, or design-system patterns that may depend on presentation for meaning. Check the DOM order, semantic structure, form relationships, and whether CSS generated content carries essential information.

Use when reviewing headers, forms, cookies, or third-party integrations related to Implement a content security policy. Validate the effective browser and HTTP behavior in a production-like environment.

Use when auditing article or blog pages for date markup, generating Article JSON-LD with datePublished/dateModified, or checking whether a CMS template surfaces dates correctly.

Use when reviewing stylesheets, component styles, and responsive behavior related to Use container queries for component-level responsiveness. Check the rendered layout across breakpoints and interaction states before proposing a fix.

Use when auditing metadata, crawlability, structured data, or indexability related to Create a comprehensive Contact page. Verify the rendered HTML and HTTP response rather than relying only on source files.

Use when reviewing scripts, client components, bundles, or runtime behavior related to Prefer const and let over var. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.

Use when reviewing scripts, client components, bundles, or runtime behavior related to Remove console statements in production. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.

Use when reviewing support UI across multi-page flows such as checkout, onboarding, account recovery, or support journeys. Compare multiple pages in the same variation instead of reviewing a single page alone.

Use when auditing slow page loads, heavy assets, or rendering delays related to Implement Google Consent Mode v2. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when auditing slow page loads, heavy assets, or rendering delays related to Enable text-based compression. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when building a design token system, creating accessible colour palettes, generating colour ramps programmatically, or migrating a design system to support wide-gamut displays.

Use when applies to all visible text and text images, UI component borders (input fields, buttons), focus indicators, icons that convey meaning, and graphical objects required to understand content. Does not apply to inactive/disabled UI components or purely decorative elements.

Use when reviewing large SPA bundles, new dependency additions, or routes that feel slow to hydrate. Focus on code that is not required for the initial view and can move behind route transitions, user interaction, or viewport-based loading.

Use when reviewing templates, rendered HTML, or shared components related to Remove comments and debug code in production. Validate the final browser-facing markup, not just the source framework abstraction.

Use when auditing metadata, crawlability, structured data, or indexability related to Cite authoritative external sources. Verify the rendered HTML and HTTP response rather than relying only on source files.

Use when reviewing templates, rendered HTML, or shared components related to Declare UTF-8 character encoding. Validate the final browser-facing markup, not just the source framework abstraction.

Use when auditing slow page loads, heavy assets, or rendering delays related to Use a content delivery network. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

Use when reviewing a CSS architecture for specificity issues, setting up a design system, or migrating a large codebase from utility-first to a layered architecture.

Use when reviewing templates, rendered HTML, or shared components related to Make carousels accessible. Validate the final browser-facing markup, not just the source framework abstraction.

Use when auditing metadata, crawlability, structured data, or indexability related to Set canonical URLs for all pages. Verify the rendered HTML and HTTP response rather than relying only on source files.

Use when auditing metadata, crawlability, structured data, or indexability related to Sync HTML canonical tags and Link headers. Verify the rendered HTML and HTTP response rather than relying only on source files.

Use when auditing metadata, crawlability, structured data, or indexability related to Avoid redirect chains on canonical URLs. Verify the rendered HTML and HTTP response rather than relying only on source files.

Use when reviewing rendered HTML, interactive components, or design-system patterns related to Provide accessible names for buttons. Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output where relevant.