# Frontend Checklist

> 385 frontend best practice rules across HTML, CSS, JavaScript, Accessibility, SEO, Security, Performance, Images, and Testing. Free, open-source.

## Use via MCP (AI Agents)

- MCP Endpoint: https://mcp.frontendchecklist.io
- MCP Docs: https://frontendchecklist.io/mcp
- VS Code: Add `https://mcp.frontendchecklist.io` to .vscode/mcp.json

```json
{
  "mcpServers": {
    "frontendchecklist": {
      "type": "http",
      "url": "https://mcp.frontendchecklist.io"
    }
  }
}
```

### MCP Tools
- review_code — Audit HTML/CSS/JS against all rules at once
- audit_url — Fetch a live URL and audit its HTML automatically
- get_workflow — Get ordered checklist for a workflow
- get_checklist_rules — Batch-fetch full rules for a checklist
- get_rule — Full details for one rule
- search_rules — Search by keyword or category
- check_rule / fix_rule / explain_rule — Rule-specific prompts
- list_categories — All categories with rule counts
- get_quick_reference — Compact priority-filtered view

## Resources

- [Rules Browser](https://frontendchecklist.io/rules)
- [Guides](https://frontendchecklist.io/guides)
- [Full Reference](https://frontendchecklist.io/llms-full.txt)
- [MCP Docs](https://frontendchecklist.io/mcp)

## Optional

- [GitHub](https://github.com/thedaviddias/Front-End-Checklist)

## Categories

- [Accessibility](https://frontendchecklist.io/rules/accessibility) — 95 rules, 9 critical, 26 high
- [Css](https://frontendchecklist.io/rules/css) — 32 rules, 11 high
- [Html](https://frontendchecklist.io/rules/html) — 25 rules, 3 critical, 9 high
- [I18n](https://frontendchecklist.io/rules/i18n) — 5 rules
- [Images](https://frontendchecklist.io/rules/images) — 25 rules, 1 critical, 15 high
- [Javascript](https://frontendchecklist.io/rules/javascript) — 26 rules, 1 critical, 12 high
- [Performance](https://frontendchecklist.io/rules/performance) — 43 rules, 1 critical, 22 high
- [Privacy](https://frontendchecklist.io/rules/privacy) — 5 rules, 2 high
- [Security](https://frontendchecklist.io/rules/security) — 22 rules, 4 critical, 10 high
- [Seo](https://frontendchecklist.io/rules/seo) — 94 rules, 19 high
- [Testing](https://frontendchecklist.io/rules/testing) — 13 rules, 7 high

## Guides

- [How to run a practical Core Web Vitals audit before launch](https://frontendchecklist.io/guides/core-web-vitals-audit-workflow) — Guide, performance
- [Why opinionated checklists still beat generic best-practice lists](https://frontendchecklist.io/guides/why-opinionated-checklists-still-beat-generic-best-practices) — Insight, seo

## Rules

### Accessibility

- [Do not use aria-hidden on the document body](https://frontendchecklist.io/rules/accessibility/aria-hidden-body) [critical]
- [Ensure all input fields have accessible names](https://frontendchecklist.io/rules/accessibility/aria-input-field-name) [critical]
- [Provide accessible names for buttons](https://frontendchecklist.io/rules/accessibility/button-name) [critical]
- [Prevent seizure-triggering flashing content](https://frontendchecklist.io/rules/accessibility/flashing-content) [critical]
- [Associate labels with form controls](https://frontendchecklist.io/rules/accessibility/form-labels) [critical]
- [Use logical heading hierarchy](https://frontendchecklist.io/rules/accessibility/heading-hierarchy) [critical]
- [Provide alt text for image buttons](https://frontendchecklist.io/rules/accessibility/input-image-alt) [critical]
- [Enable keyboard navigation for all elements](https://frontendchecklist.io/rules/accessibility/keyboard-navigation) [critical]
- [Support content reflow at 400% zoom](https://frontendchecklist.io/rules/accessibility/zoom-reflow) [critical]
- [Provide accessible authentication methods](https://frontendchecklist.io/rules/accessibility/accessible-authentication) [high]
- [Provide accessible names for all interactive elements](https://frontendchecklist.io/rules/accessibility/aria-labels) [high]
- [Announce dynamic content with ARIA live regions](https://frontendchecklist.io/rules/accessibility/aria-live-regions) [high]
- [Ensure ARIA roles contain required child roles](https://frontendchecklist.io/rules/accessibility/aria-required-children) [high]
- [Ensure ARIA attributes are valid](https://frontendchecklist.io/rules/accessibility/aria-valid-attr) [high]
- [Avoid autoplaying media](https://frontendchecklist.io/rules/accessibility/autoplay-media) [high]
- [Meet minimum color contrast ratios](https://frontendchecklist.io/rules/accessibility/color-contrast) [high]
- [Ensure content remains usable without CSS](https://frontendchecklist.io/rules/accessibility/content-without-css) [high]
- [Use unique IDs for active elements](https://frontendchecklist.io/rules/accessibility/duplicate-id-active) [high]
- [Use unique IDs for ARIA references](https://frontendchecklist.io/rules/accessibility/duplicate-id-aria) [high]
- [Manage focus during dynamic interactions](https://frontendchecklist.io/rules/accessibility/focus-management) [high]
- [Keep focused elements unobscured](https://frontendchecklist.io/rules/accessibility/focus-not-obscured) [high]
- [Ensure logical focus order](https://frontendchecklist.io/rules/accessibility/focus-order) [high]
- [Use descriptive link text](https://frontendchecklist.io/rules/accessibility/link-text) [high]
- [Make modal dialogs keyboard accessible](https://frontendchecklist.io/rules/accessibility/modal-accessibility) [high]
- [Support both portrait and landscape orientation](https://frontendchecklist.io/rules/accessibility/orientation) [high]
- [Respect reduced motion preferences](https://frontendchecklist.io/rules/accessibility/reduced-motion) [high]
- [Avoid redundant entry in the same process](https://frontendchecklist.io/rules/accessibility/redundant-entry) [high]
- [Test with screen readers](https://frontendchecklist.io/rules/accessibility/screen-reader-testing) [high]
- [Avoid sensory-only instructions](https://frontendchecklist.io/rules/accessibility/sensory-instructions) [high]
- [Prevent data loss from session timeouts](https://frontendchecklist.io/rules/accessibility/session-timeout-recovery) [high]
- [Include a skip navigation link](https://frontendchecklist.io/rules/accessibility/skip-navigation) [high]
- [Support text resizing to 200%](https://frontendchecklist.io/rules/accessibility/text-resizing) [high]
- [Provide captions for video content](https://frontendchecklist.io/rules/accessibility/video-captions) [high]
- [Make notifications accessible](https://frontendchecklist.io/rules/accessibility/accessible-notifications) [high]
- [Use navigation landmark regions](https://frontendchecklist.io/rules/accessibility/navigation-landmark) [high]
- [Use semantic table markup for screen readers](https://frontendchecklist.io/rules/accessibility/accessible-tables)
- [Ensure accesskey values are unique](https://frontendchecklist.io/rules/accessibility/accesskeys)
- [Use only allowed ARIA attributes for each role](https://frontendchecklist.io/rules/accessibility/aria-allowed-attr)
- [Provide accessible names for ARIA command elements](https://frontendchecklist.io/rules/accessibility/aria-command-name)
- [Avoid using deprecated ARIA roles](https://frontendchecklist.io/rules/accessibility/aria-deprecated-role)
- [Ensure dialogs have an accessible name](https://frontendchecklist.io/rules/accessibility/aria-dialog-name)
- [Remove focusable elements from aria-hidden containers](https://frontendchecklist.io/rules/accessibility/aria-hidden-focus)
- [Provide accessible names for meter elements](https://frontendchecklist.io/rules/accessibility/aria-meter-name)
- [Provide accessible names for progress bars](https://frontendchecklist.io/rules/accessibility/aria-progressbar-name)
- [Include required ARIA attributes for roles](https://frontendchecklist.io/rules/accessibility/aria-required-attr)
- [Ensure ARIA roles are contained by required parent roles](https://frontendchecklist.io/rules/accessibility/aria-required-parent)
- [Use valid ARIA role values](https://frontendchecklist.io/rules/accessibility/aria-roles)
- [Avoid focusable descendants in role="text" elements](https://frontendchecklist.io/rules/accessibility/aria-text)
- [Provide accessible names for toggle fields](https://frontendchecklist.io/rules/accessibility/aria-toggle-field-name)
- [Provide accessible names for tooltips](https://frontendchecklist.io/rules/accessibility/aria-tooltip-name)
- [Provide accessible names for tree items](https://frontendchecklist.io/rules/accessibility/aria-treeitem-name)
- [Use valid values for ARIA attributes](https://frontendchecklist.io/rules/accessibility/aria-valid-attr-value)
- [Provide audio descriptions for video](https://frontendchecklist.io/rules/accessibility/audio-descriptions)
- [Keep repeated help mechanisms in a consistent location](https://frontendchecklist.io/rules/accessibility/consistent-help)
- [Hide decorative elements from assistive technology](https://frontendchecklist.io/rules/accessibility/decorative-elements)
- [Use correct definition list structure](https://frontendchecklist.io/rules/accessibility/definition-list)
- [Wrap definition items in a definition list](https://frontendchecklist.io/rules/accessibility/dlitem)
- [Ensure headings contain text](https://frontendchecklist.io/rules/accessibility/empty-heading)
- [Fix empty and broken links](https://frontendchecklist.io/rules/accessibility/empty-links)
- [Use a single label for each form field](https://frontendchecklist.io/rules/accessibility/form-field-multiple-labels)
- [Provide titles for iframes and frames](https://frontendchecklist.io/rules/accessibility/frame-title)
- [Maintain logical heading order](https://frontendchecklist.io/rules/accessibility/heading-order)
- [Match lang and xml:lang attributes](https://frontendchecklist.io/rules/accessibility/html-xml-lang-mismatch)
- [Ensure identical links have consistent destinations](https://frontendchecklist.io/rules/accessibility/identical-links-same-purpose)
- [Use inclusive language](https://frontendchecklist.io/rules/accessibility/inclusive-language)
- [Align visible labels with accessible names](https://frontendchecklist.io/rules/accessibility/label-content-name-mismatch)
- [Use exactly one main landmark](https://frontendchecklist.io/rules/accessibility/landmark-one-main)
- [Use landmark regions correctly](https://frontendchecklist.io/rules/accessibility/landmark-regions)
- [Make links in text blocks visually distinguishable](https://frontendchecklist.io/rules/accessibility/link-in-text-block)
- [Use correct list structure](https://frontendchecklist.io/rules/accessibility/list-structure)
- [Place list items within list containers](https://frontendchecklist.io/rules/accessibility/listitem)
- [Avoid meta refresh redirects](https://frontendchecklist.io/rules/accessibility/meta-refresh)
- [Provide alternative text for objects](https://frontendchecklist.io/rules/accessibility/object-alt)
- [Provide alternatives to parallax effects](https://frontendchecklist.io/rules/accessibility/parallax-effects)
- [Allow pasting into form inputs](https://frontendchecklist.io/rules/accessibility/paste-inputs)
- [Write in plain language](https://frontendchecklist.io/rules/accessibility/plain-language)
- [Avoid scrolljacking and custom scroll behavior](https://frontendchecklist.io/rules/accessibility/scrolljacking)
- [Provide accessible names for select elements](https://frontendchecklist.io/rules/accessibility/select-name)
- [Use semantic list elements](https://frontendchecklist.io/rules/accessibility/semantic-lists)
- [Implement "Skip to Content" links](https://frontendchecklist.io/rules/accessibility/skip-link)
- [Use appropriate tabindex values](https://frontendchecklist.io/rules/accessibility/tabindex)
- [Ensure tables have unique accessible names](https://frontendchecklist.io/rules/accessibility/table-duplicate-name)
- [Define proper table headers](https://frontendchecklist.io/rules/accessibility/table-headers)
- [Link table cells to headers using IDs](https://frontendchecklist.io/rules/accessibility/td-headers-attr)
- [Ensure table headers associate with data cells](https://frontendchecklist.io/rules/accessibility/th-has-data-cells)
- [Provide sufficient touch target size](https://frontendchecklist.io/rules/accessibility/touch-targets)
- [Create accessible tooltips](https://frontendchecklist.io/rules/accessibility/accessible-tooltips)
- [Make accordions keyboard navigable](https://frontendchecklist.io/rules/accessibility/accordion-accessibility)
- [Make carousels accessible](https://frontendchecklist.io/rules/accessibility/carousel-accessibility)
- [Make drag and drop accessible](https://frontendchecklist.io/rules/accessibility/draggable-accessibility)
- [Make tabs keyboard navigable](https://frontendchecklist.io/rules/accessibility/tabs-accessibility)
- [Provide instant anchor scroll option](https://frontendchecklist.io/rules/accessibility/anchor-smooth-scroll)
- [Avoid autofocus on form fields](https://frontendchecklist.io/rules/accessibility/autofocus-avoidance)
- [Avoid redundant image alternative text](https://frontendchecklist.io/rules/accessibility/image-redundant-alt)
- [Avoid images of text](https://frontendchecklist.io/rules/accessibility/text-in-images)

### Css

- [Do not disable pinch zoom](https://frontendchecklist.io/rules/css/viewport-zoom) [high]
- [Use transform and opacity for animations](https://frontendchecklist.io/rules/css/animation-performance) [high]
- [Inline critical CSS for faster rendering](https://frontendchecklist.io/rules/css/css-critical) [high]
- [Use CSS custom properties for design tokens](https://frontendchecklist.io/rules/css/css-custom-properties) [high]
- [Minify all CSS files](https://frontendchecklist.io/rules/css/css-minification) [high]
- [Load CSS without blocking render](https://frontendchecklist.io/rules/css/css-non-blocking) [high]
- [Avoid embedded and inline CSS](https://frontendchecklist.io/rules/css/embedded-or-inline-css) [high]
- [Provide visible custom focus indicators](https://frontendchecklist.io/rules/css/focus-styles) [high]
- [Use relative units for responsive layouts](https://frontendchecklist.io/rules/css/responsive-units) [high]
- [Keep CSS specificity low and flat](https://frontendchecklist.io/rules/css/specificity-management) [high]
- [Remove unused CSS rules](https://frontendchecklist.io/rules/css/unused-css) [high]
- [Use container queries for component-level responsiveness](https://frontendchecklist.io/rules/css/container-queries)
- [Use CSS containment to limit repaint scope](https://frontendchecklist.io/rules/css/css-containment)
- [Use CSS Grid for two-dimensional layouts](https://frontendchecklist.io/rules/css/css-grid)
- [Order CSS files correctly](https://frontendchecklist.io/rules/css/css-order)
- [Include a print stylesheet](https://frontendchecklist.io/rules/css/css-print)
- [Support dark mode with prefers-color-scheme](https://frontendchecklist.io/rules/css/dark-mode-css)
- [Apply Flexbox best practices](https://frontendchecklist.io/rules/css/flexbox-patterns)
- [Use readable font sizes on mobile](https://frontendchecklist.io/rules/css/font-size)
- [Prevent horizontal scrolling](https://frontendchecklist.io/rules/css/horizontal-scroll)
- [Avoid intrusive interstitials](https://frontendchecklist.io/rules/css/interstitials)
- [Use CSS logical properties for i18n and RTL support](https://frontendchecklist.io/rules/css/logical-properties)
- [Use consistent CSS naming conventions](https://frontendchecklist.io/rules/css/naming-conventions)
- [Use a CSS reset or normalize stylesheet](https://frontendchecklist.io/rules/css/reset-css)
- [Lint CSS and SCSS files](https://frontendchecklist.io/rules/css/styles-lint)
- [Optimize web font formats](https://frontendchecklist.io/rules/css/webfont-format)
- [Use @layer to manage CSS cascade order explicitly](https://frontendchecklist.io/rules/css/cascade-layers)
- [Use oklch() and oklab() for perceptually uniform colour palettes](https://frontendchecklist.io/rules/css/color-oklch)
- [Register CSS custom properties with @property for animation and type safety](https://frontendchecklist.io/rules/css/css-at-property)
- [Use :has() to style parent elements based on their descendants](https://frontendchecklist.io/rules/css/has-selector)
- [Use CSS subgrid to align nested grid items to parent tracks](https://frontendchecklist.io/rules/css/subgrid)
- [Use the View Transitions API for smooth page and component transitions](https://frontendchecklist.io/rules/css/view-transitions)

### Html

- [Declare UTF-8 character encoding](https://frontendchecklist.io/rules/html/charset) [critical]
- [Use the HTML5 doctype](https://frontendchecklist.io/rules/html/doctype) [critical]
- [Set the responsive viewport meta tag](https://frontendchecklist.io/rules/html/viewport) [critical]
- [Load scripts with defer, async, or type=module](https://frontendchecklist.io/rules/html/defer-async) [high]
- [Validate forms accessibly](https://frontendchecklist.io/rules/html/form-validation) [high]
- [Use semantic HTML elements](https://frontendchecklist.io/rules/html/html5-semantic-elements) [high]
- [Use semantic input type attributes](https://frontendchecklist.io/rules/html/input-types) [high]
- [Set the page lang attribute](https://frontendchecklist.io/rules/html/lang-attribute) [high]
- [Add Subresource Integrity to external scripts](https://frontendchecklist.io/rules/html/subresource-integrity) [high]
- [Ensure all IDs are unique](https://frontendchecklist.io/rules/html/unique-id) [high]
- [Make videos accessible with captions](https://frontendchecklist.io/rules/html/video-accessibility) [high]
- [Validate HTML against W3C standards](https://frontendchecklist.io/rules/html/w3c-compliant) [high]
- [Create a custom 404 error page](https://frontendchecklist.io/rules/html/404-page)
- [Implement accessible breadcrumb navigation](https://frontendchecklist.io/rules/html/breadcrumb-navigation)
- [Remove comments and debug code in production](https://frontendchecklist.io/rules/html/clean-up-comments)
- [Make custom elements and Web Components accessible](https://frontendchecklist.io/rules/html/custom-element-accessibility)
- [Set text direction for RTL languages](https://frontendchecklist.io/rules/html/direction-attribute)
- [Implement favicons for all devices](https://frontendchecklist.io/rules/html/favicons)
- [Make file uploads accessible](https://frontendchecklist.io/rules/html/file-upload-accessibility)
- [Provide noscript fallback content](https://frontendchecklist.io/rules/html/noscript-tag)
- [Make pagination accessible](https://frontendchecklist.io/rules/html/pagination-accessibility)
- [Make search inputs accessible](https://frontendchecklist.io/rules/html/search-input)
- [Add thumbnail images to videos](https://frontendchecklist.io/rules/html/video-thumbnail)
- [Link a Web App Manifest for installability](https://frontendchecklist.io/rules/html/web-app-manifest)
- [Meet PWA installability criteria](https://frontendchecklist.io/rules/html/pwa-installability)

### I18n

- [Use Intl APIs for currency, number, and date formatting](https://frontendchecklist.io/rules/i18n/currency-formatting)
- [Add hreflang tags for multilingual sites](https://frontendchecklist.io/rules/i18n/hreflang)
- [Handle plural forms with Intl.PluralRules or ICU MessageFormat](https://frontendchecklist.io/rules/i18n/pluralization)
- [Design UI components to accommodate text expansion from translation](https://frontendchecklist.io/rules/i18n/text-expansion)
- [Use locale-neutral images and provide cultural overrides when needed](https://frontendchecklist.io/rules/i18n/locale-images)

### Images

- [Provide meaningful alt text for images](https://frontendchecklist.io/rules/images/alt-text) [critical]
- [Fix broken images](https://frontendchecklist.io/rules/images/broken-images) [high]
- [Prioritize loading critical images](https://frontendchecklist.io/rules/images/critical-images) [high]
- [Set explicit width and height on images](https://frontendchecklist.io/rules/images/dimensions) [high]
- [Serve images from a CDN](https://frontendchecklist.io/rules/images/image-cdn) [high]
- [Compress images without quality loss](https://frontendchecklist.io/rules/images/image-compression) [high]
- [Keep image file sizes within recommended limits](https://frontendchecklist.io/rules/images/image-file-size) [high]
- [Optimize all images for web](https://frontendchecklist.io/rules/images/image-optimization) [high]
- [Use modern image formats (WebP, AVIF)](https://frontendchecklist.io/rules/images/modern-format) [high]
- [Lazy load offscreen images](https://frontendchecklist.io/rules/images/offscreen-lazy) [high]
- [Optimise images for faster loading](https://frontendchecklist.io/rules/images/optimized) [high]
- [Use <picture> with an <img> fallback](https://frontendchecklist.io/rules/images/picture-element) [high]
- [Implement responsive images with srcset](https://frontendchecklist.io/rules/images/responsive-images) [high]
- [Serve images at the correct display size](https://frontendchecklist.io/rules/images/responsive-size) [high]
- [Use srcset for responsive images](https://frontendchecklist.io/rules/images/srcset) [high]
- [Use WebP format with fallbacks](https://frontendchecklist.io/rules/images/webp-format) [high]
- [Use AVIF format for modern browsers](https://frontendchecklist.io/rules/images/avif-format)
- [Use <figure> and <figcaption> for image captions](https://frontendchecklist.io/rules/images/figure-figcaption)
- [Support high-DPI retina displays](https://frontendchecklist.io/rules/images/retina-display)
- [Manage inline SVG size and complexity](https://frontendchecklist.io/rules/images/svg-inline)
- [Optimize SVG files](https://frontendchecklist.io/rules/images/svg-optimization)
- [Handle image loading errors gracefully](https://frontendchecklist.io/rules/images/error-images)
- [Use descriptive image filenames](https://frontendchecklist.io/rules/images/filename-quality)
- [Use progressive JPEG encoding](https://frontendchecklist.io/rules/images/progressive-jpeg)
- [Use image sprites where appropriate](https://frontendchecklist.io/rules/images/sprite-generation)

### Javascript

- [Never use eval() or unsafe dynamic code execution](https://frontendchecklist.io/rules/javascript/avoid-eval) [critical]
- [Split large JavaScript bundles](https://frontendchecklist.io/rules/javascript/code-splitting) [high]
- [Prefer const and let over var](https://frontendchecklist.io/rules/javascript/const-let) [high]
- [Handle cross-origin requests securely](https://frontendchecklist.io/rules/javascript/cross-origin-security) [high]
- [Debounce and throttle event handlers](https://frontendchecklist.io/rules/javascript/debounce-throttle) [high]
- [Minimize costly DOM read/write operations](https://frontendchecklist.io/rules/javascript/dom-performance) [high]
- [Implement proper error handling](https://frontendchecklist.io/rules/javascript/error-handling) [high]
- [Use ES modules (import/export)](https://frontendchecklist.io/rules/javascript/es-modules) [high]
- [Avoid inline JavaScript](https://frontendchecklist.io/rules/javascript/javascript-inline) [high]
- [Minify all JavaScript files](https://frontendchecklist.io/rules/javascript/javascript-minification) [high]
- [Prevent common memory leak patterns](https://frontendchecklist.io/rules/javascript/memory-leaks) [high]
- [Validate external data at runtime with a schema library](https://frontendchecklist.io/rules/javascript/runtime-validation) [high]
- [Enable TypeScript strict mode in tsconfig.json](https://frontendchecklist.io/rules/javascript/typescript-strict-mode) [high]
- [Remove console statements in production](https://frontendchecklist.io/rules/javascript/console-cleanup)
- [Use event delegation for dynamic content](https://frontendchecklist.io/rules/javascript/event-delegation)
- [Prefer immutable data patterns](https://frontendchecklist.io/rules/javascript/immutable-patterns)
- [Lint JavaScript code](https://frontendchecklist.io/rules/javascript/javascript-linter)
- [Parse JSON safely with error handling](https://frontendchecklist.io/rules/javascript/json-safety)
- [Use modern array and object methods](https://frontendchecklist.io/rules/javascript/modern-array-methods)
- [Avoid the any type — use unknown, generics, or type guards instead](https://frontendchecklist.io/rules/javascript/no-explicit-any)
- [Enable noUncheckedIndexedAccess to catch out-of-bounds array bugs](https://frontendchecklist.io/rules/javascript/no-unchecked-indexed-access)
- [Use scheduler.yield() to keep the main thread responsive during long tasks](https://frontendchecklist.io/rules/javascript/scheduler-yield)
- [Write internationalisation-friendly translation strings](https://frontendchecklist.io/rules/javascript/translation-strings)
- [Avoid implicit type coercion](https://frontendchecklist.io/rules/javascript/type-coercion)
- [Use Web Storage API safely](https://frontendchecklist.io/rules/javascript/web-storage)
- [Use import type for type-only imports](https://frontendchecklist.io/rules/javascript/type-only-imports)

### Performance

- [Optimize largest contentful paint](https://frontendchecklist.io/rules/performance/largest-contentful-paint) [critical]
- [Analyze performance with WebPageTest](https://frontendchecklist.io/rules/performance/webpagetest) [high]
- [Optimize pages for back/forward cache](https://frontendchecklist.io/rules/performance/back-forward-cache) [high]
- [Enable browser caching](https://frontendchecklist.io/rules/performance/browser-caching) [high]
- [Use a content delivery network](https://frontendchecklist.io/rules/performance/cdn) [high]
- [Enable text-based compression](https://frontendchecklist.io/rules/performance/compression) [high]
- [Implement Google Consent Mode v2](https://frontendchecklist.io/rules/performance/consent-mode) [high]
- [Minimize critical request chains](https://frontendchecklist.io/rules/performance/critical-request-chains) [high]
- [Minimize cumulative layout shift](https://frontendchecklist.io/rules/performance/cumulative-layout-shift) [high]
- [Optimize first contentful paint](https://frontendchecklist.io/rules/performance/first-contentful-paint) [high]
- [Optimize web font loading](https://frontendchecklist.io/rules/performance/font-loading) [high]
- [Minimize HTTP requests](https://frontendchecklist.io/rules/performance/http-requests) [high]
- [Enable HTTP/2 or HTTP/3](https://frontendchecklist.io/rules/performance/http2) [high]
- [Load non-critical code on user interaction](https://frontendchecklist.io/rules/performance/import-on-interaction) [high]
- [Load non-critical code when content approaches the viewport](https://frontendchecklist.io/rules/performance/import-on-visibility) [high]
- [Optimize interaction to next paint](https://frontendchecklist.io/rules/performance/interaction-to-next-paint) [high]
- [Implement lazy loading for offscreen content](https://frontendchecklist.io/rules/performance/lazy-loading) [high]
- [Virtualize long lists and tables](https://frontendchecklist.io/rules/performance/list-virtualization) [high]
- [Show loading indicators](https://frontendchecklist.io/rules/performance/loading-indicators) [high]
- [Keep page load time under 3 seconds](https://frontendchecklist.io/rules/performance/page-load-time) [high]
- [Keep page weight under 1500KB](https://frontendchecklist.io/rules/performance/page-weight) [high]
- [Use resource hints for faster loading](https://frontendchecklist.io/rules/performance/resource-hints) [high]
- [Optimize third-party script loading](https://frontendchecklist.io/rules/performance/third-party-scripts) [high]
- [Convert animated GIFs to video](https://frontendchecklist.io/rules/performance/animated-content)
- [Perform browser-based performance audits](https://frontendchecklist.io/rules/performance/browser-required)
- [Optimize CSS file size](https://frontendchecklist.io/rules/performance/css-file-size)
- [Reduce DOM size and complexity](https://frontendchecklist.io/rules/performance/dom-size)
- [Remove duplicate JavaScript libraries](https://frontendchecklist.io/rules/performance/duplicate-js)
- [Use fetchpriority to hint resource loading priority](https://frontendchecklist.io/rules/performance/fetchpriority-attribute)
- [Optimize Google Tag Manager implementation](https://frontendchecklist.io/rules/performance/gtm-present)
- [Optimize JavaScript bundle size](https://frontendchecklist.io/rules/performance/js-file-size)
- [Use secure and up-to-date JS libraries](https://frontendchecklist.io/rules/performance/js-libraries)
- [Avoid JavaScript-based redirects](https://frontendchecklist.io/rules/performance/js-redirects)
- [Disable lazy loading for above-the-fold content](https://frontendchecklist.io/rules/performance/lazy-above-fold)
- [Avoid serving legacy JavaScript to modern browsers](https://frontendchecklist.io/rules/performance/legacy-js)
- [Use preconnect for critical third-party origins](https://frontendchecklist.io/rules/performance/preconnect)
- [Eliminate render-blocking resources](https://frontendchecklist.io/rules/performance/render-blocking)
- [Register a service worker for caching and offline support](https://frontendchecklist.io/rules/performance/service-worker)
- [Provide source maps for production debugging](https://frontendchecklist.io/rules/performance/source-maps)
- [Stream HTML to the browser before the full response is ready](https://frontendchecklist.io/rules/performance/streaming-html)
- [Reduce Time to First Byte (TTFB)](https://frontendchecklist.io/rules/performance/ttfb)
- [Provide an offline fallback page](https://frontendchecklist.io/rules/performance/offline-fallback)
- [Use the Speculation Rules API to prefetch and prerender navigations](https://frontendchecklist.io/rules/performance/speculation-rules)

### Privacy

- [Show a cookie consent notice](https://frontendchecklist.io/rules/privacy/cookie-consent) [high]
- [Link to your privacy policy in the footer](https://frontendchecklist.io/rules/privacy/privacy-policy) [high]
- [Collect only the minimum personal data necessary](https://frontendchecklist.io/rules/privacy/data-minimisation)
- [Implement a user-facing data deletion mechanism](https://frontendchecklist.io/rules/privacy/right-to-erasure)
- [Avoid third-party cookies](https://frontendchecklist.io/rules/privacy/third-party-cookies)

### Security

- [Submit forms over HTTPS](https://frontendchecklist.io/rules/security/form-https) [critical]
- [Redirect HTTP to HTTPS](https://frontendchecklist.io/rules/security/http-to-https) [critical]
- [Serve all pages over HTTPS](https://frontendchecklist.io/rules/security/https) [critical]
- [Leaked Environment Variables](https://frontendchecklist.io/rules/security/leaked-secrets) [critical]
- [Implement a content security policy](https://frontendchecklist.io/rules/security/content-security-policy) [high]
- [Audit dependencies for known vulnerabilities](https://frontendchecklist.io/rules/security/dependency-audit) [high]
- [Set an HSTS header](https://frontendchecklist.io/rules/security/hsts) [high]
- [Avoid mixed content on HTTPS pages](https://frontendchecklist.io/rules/security/mixed-content) [high]
- [Secure password input fields](https://frontendchecklist.io/rules/security/password-field-security) [high]
- [Set Secure, HttpOnly, and SameSite flags on session cookies](https://frontendchecklist.io/rules/security/session-cookie-flags) [high]
- [Prevent stack trace exposure in production error responses](https://frontendchecklist.io/rules/security/stack-trace-exposure) [high]
- [Store authentication tokens securely](https://frontendchecklist.io/rules/security/token-storage-security) [high]
- [Set X-Content-Type-Options: nosniff](https://frontendchecklist.io/rules/security/x-content-type) [high]
- [Set an X-Frame-Options header](https://frontendchecklist.io/rules/security/x-frame-options) [high]
- [Use COOP, COEP, and CORP for cross-origin isolation when needed](https://frontendchecklist.io/rules/security/cross-origin-isolation)
- [Protect public forms with CAPTCHA](https://frontendchecklist.io/rules/security/form-captcha)
- [External Link Security](https://frontendchecklist.io/rules/security/new-tab)
- [Set a Permissions-Policy header](https://frontendchecklist.io/rules/security/permissions-policy)
- [Set a Referrer-Policy header](https://frontendchecklist.io/rules/security/referrer-policy)
- [Link to your terms of service in the footer](https://frontendchecklist.io/rules/security/terms-of-service)
- [Blocked Tracking Links](https://frontendchecklist.io/rules/security/blocked-links)
- [Adblock Element Hiding](https://frontendchecklist.io/rules/security/element-hiding)

### Seo

- [Implement valid Article structured data](https://frontendchecklist.io/rules/seo/article) [high]
- [Resolve internal broken links](https://frontendchecklist.io/rules/seo/broken-links) [high]
- [Set canonical URLs for all pages](https://frontendchecklist.io/rules/seo/canonical-url) [high]
- [Write a meta description for each page](https://frontendchecklist.io/rules/seo/meta-description) [high]
- [Meta Tags in Body](https://frontendchecklist.io/rules/seo/meta-in-body) [high]
- [Write a descriptive page title](https://frontendchecklist.io/rules/seo/meta-title) [high]
- [Noindex in Sitemap](https://frontendchecklist.io/rules/seo/noindex-in-sitemap) [high]
- [Publish high-quality content](https://frontendchecklist.io/rules/seo/quality) [high]
- [Avoid multi-hop redirect chains](https://frontendchecklist.io/rules/seo/redirect-chain) [high]
- [Robots Meta Conflict](https://frontendchecklist.io/rules/seo/robots-meta-conflict) [high]
- [Set robots meta directives correctly](https://frontendchecklist.io/rules/seo/robots-meta) [high]
- [Publish a robots.txt file](https://frontendchecklist.io/rules/seo/robots-txt) [high]
- [Schema + Noindex Conflict](https://frontendchecklist.io/rules/seo/schema-noindex-conflict) [high]
- [4XX Pages in Sitemap](https://frontendchecklist.io/rules/seo/sitemap-4xx) [high]
- [Keep XML sitemaps valid](https://frontendchecklist.io/rules/seo/sitemap-valid) [high]
- [Create and submit an XML sitemap](https://frontendchecklist.io/rules/seo/sitemap) [high]
- [Add structured data markup](https://frontendchecklist.io/rules/seo/structured-data) [high]
- [Keep page titles unique](https://frontendchecklist.io/rules/seo/title-unique) [high]
- [Identify YMYL content on your site](https://frontendchecklist.io/rules/seo/ymyl-detection) [high]
- [Check for broken links](https://frontendchecklist.io/rules/seo/link-checker)
- [Create a dedicated About page](https://frontendchecklist.io/rules/seo/about-page)
- [Provide clear affiliate disclosures](https://frontendchecklist.io/rules/seo/affiliate-disclosure)
- [Audit and refine AI-generated content](https://frontendchecklist.io/rules/seo/ai-content)
- [Audit all noindex pages](https://frontendchecklist.io/rules/seo/all-noindex-pages)
- [Use descriptive anchor text](https://frontendchecklist.io/rules/seo/anchor-text)
- [Optimize article link density](https://frontendchecklist.io/rules/seo/article-links)
- [Display clear author bylines](https://frontendchecklist.io/rules/seo/author-byline)
- [Highlight author credentials and expertise](https://frontendchecklist.io/rules/seo/author-expertise)
- [Implement comprehensive author markup](https://frontendchecklist.io/rules/seo/author-info)
- [Implement valid BreadcrumbList schema](https://frontendchecklist.io/rules/seo/breadcrumb)
- [Fix or remove broken external links](https://frontendchecklist.io/rules/seo/broken-external-links)
- [Fix malformed HTML structure](https://frontendchecklist.io/rules/seo/broken-html)
- [Avoid redirect chains on canonical URLs](https://frontendchecklist.io/rules/seo/canonical-chain)
- [Sync HTML canonical tags and Link headers](https://frontendchecklist.io/rules/seo/canonical-header)
- [Cite authoritative external sources](https://frontendchecklist.io/rules/seo/citations)
- [Create a comprehensive Contact page](https://frontendchecklist.io/rules/seo/contact-page)
- [Show published and updated dates](https://frontendchecklist.io/rules/seo/content-dates)
- [Add outgoing links to dead-end pages](https://frontendchecklist.io/rules/seo/dead-end-pages)
- [Add disclaimers to sensitive content](https://frontendchecklist.io/rules/seo/disclaimers)
- [Avoid duplicate meta descriptions](https://frontendchecklist.io/rules/seo/duplicate-description)
- [Publish an editorial policy page](https://frontendchecklist.io/rules/seo/editorial-policy)
- [Add relevant external links](https://frontendchecklist.io/rules/seo/external-links)
- [Add FAQPage schema markup](https://frontendchecklist.io/rules/seo/faq)
- [Add a favicon to every page](https://frontendchecklist.io/rules/seo/favicon)
- [Show content freshness signals](https://frontendchecklist.io/rules/seo/freshness)
- [Geo Meta Tags](https://frontendchecklist.io/rules/seo/geo-meta)
- [Use a single descriptive H1](https://frontendchecklist.io/rules/seo/h1)
- [Keep HTML documents under crawl limits](https://frontendchecklist.io/rules/seo/html-size)
- [Do not link from HTTPS to HTTP](https://frontendchecklist.io/rules/seo/https-downgrade)
- [Use hyphens in URLs](https://frontendchecklist.io/rules/seo/hyphens)
- [Avoid conflicting indexability signals](https://frontendchecklist.io/rules/seo/indexability-conflicts)
- [Make important pages indexable](https://frontendchecklist.io/rules/seo/indexability)
- [Add internal links to key pages](https://frontendchecklist.io/rules/seo/internal-links)
- [Fix invalid links](https://frontendchecklist.io/rules/seo/invalid-links)
- [Use valid JSON-LD structured data](https://frontendchecklist.io/rules/seo/json-ld-valid)
- [Avoid keyword stuffing](https://frontendchecklist.io/rules/seo/keyword-stuffing)
- [Keep URLs concise](https://frontendchecklist.io/rules/seo/length)
- [Make content easy for LLMs to parse](https://frontendchecklist.io/rules/seo/llm-parsability)
- [Publish llms.txt for documentation-heavy sites](https://frontendchecklist.io/rules/seo/llms-txt)
- [Add LocalBusiness schema markup](https://frontendchecklist.io/rules/seo/local-business)
- [Use lowercase URLs](https://frontendchecklist.io/rules/seo/lowercase)
- [MIME Type Validation](https://frontendchecklist.io/rules/seo/mime-type)
- [Keep NAP details consistent](https://frontendchecklist.io/rules/seo/nap-consistency)
- [Avoid nofollow on internal links](https://frontendchecklist.io/rules/seo/nofollow-internal)
- [Avoid nosnippet on important pages](https://frontendchecklist.io/rules/seo/nosnippet)
- [OG Image Size](https://frontendchecklist.io/rules/seo/og-image-size)
- [Open Graph Tags](https://frontendchecklist.io/rules/seo/og-tags)
- [OG URL Match](https://frontendchecklist.io/rules/seo/og-url-match)
- [Add Organization schema markup](https://frontendchecklist.io/rules/seo/organization)
- [Add internal links to orphan pages](https://frontendchecklist.io/rules/seo/orphan-pages)
- [Use canonicals on paginated pages](https://frontendchecklist.io/rules/seo/pagination)
- [Limit unnecessary URL parameters](https://frontendchecklist.io/rules/seo/parameters)
- [Keep linked PDFs under 60 MB](https://frontendchecklist.io/rules/seo/pdf-size)
- [Display a physical business address](https://frontendchecklist.io/rules/seo/physical-address)
- [Add Product schema markup](https://frontendchecklist.io/rules/seo/product)
- [Write at a clear reading level](https://frontendchecklist.io/rules/seo/reading-level)
- [Link directly to final destination URLs](https://frontendchecklist.io/rules/seo/redirect-chains)
- [Add Review schema markup](https://frontendchecklist.io/rules/seo/review)
- [Service Area Pages](https://frontendchecklist.io/rules/seo/service-area)
- [Include indexable pages in your sitemap](https://frontendchecklist.io/rules/seo/sitemap-coverage)
- [Keep sitemap URLs on the correct domain](https://frontendchecklist.io/rules/seo/sitemap-domain)
- [Include keywords in URL slugs](https://frontendchecklist.io/rules/seo/slug-keywords)
- [URL Special Characters](https://frontendchecklist.io/rules/seo/special-chars)
- [Tel & Mailto Links](https://frontendchecklist.io/rules/seo/tel-mailto)
- [Use trailing slashes consistently](https://frontendchecklist.io/rules/seo/trailing-slash)
- [Show trust signals on key pages](https://frontendchecklist.io/rules/seo/trust-signals)
- [Add Twitter Card meta tags](https://frontendchecklist.io/rules/seo/twitter-cards)
- [Add VideoObject schema to video pages](https://frontendchecklist.io/rules/seo/video)
- [Weak Internal Links](https://frontendchecklist.io/rules/seo/weak-internal-links)
- [Avoid thin content on key pages](https://frontendchecklist.io/rules/seo/word-count)
- [Add share buttons to content pages](https://frontendchecklist.io/rules/seo/share-buttons)
- [Link to active social profiles](https://frontendchecklist.io/rules/seo/social-profiles)
- [URL Stop Words](https://frontendchecklist.io/rules/seo/stop-words)
- [WebSite Search Schema](https://frontendchecklist.io/rules/seo/website-search)

### Testing

- [Include accessibility testing](https://frontendchecklist.io/rules/testing/accessibility-testing) [high]
- [Test across all major browsers](https://frontendchecklist.io/rules/testing/cross-browser-testing) [high]
- [Implement end-to-end testing](https://frontendchecklist.io/rules/testing/e2e-testing) [high]
- [Integrate real-time error monitoring in production](https://frontendchecklist.io/rules/testing/error-monitoring) [high]
- [Write integration tests for key workflows](https://frontendchecklist.io/rules/testing/integration-testing) [high]
- [Test on real mobile devices and viewports](https://frontendchecklist.io/rules/testing/mobile-testing) [high]
- [Write unit tests](https://frontendchecklist.io/rules/testing/unit-tests) [high]
- [Implement consumer-driven contract testing for API boundaries](https://frontendchecklist.io/rules/testing/contract-testing)
- [Follow mocking best practices](https://frontendchecklist.io/rules/testing/mock-best-practices)
- [Use mutation testing to measure how well tests detect bugs](https://frontendchecklist.io/rules/testing/mutation-testing)
- [Enforce performance budgets in CI](https://frontendchecklist.io/rules/testing/performance-budget)
- [Maintain test coverage thresholds](https://frontendchecklist.io/rules/testing/test-coverage)
- [Use visual regression testing](https://frontendchecklist.io/rules/testing/visual-regression)

---

For full rule content including descriptions, AI prompts, and automation guidance: https://frontendchecklist.io/llms-full.txt