Modern Web Guidance

JetBrainsOfficialCreated by Google ChromeDistributed by JetBrains

Skill
Tool integration
Software development
Apache-2.0
Low risk

From the author

Search tool for modern web development best practices. MANDATORY: Execute FIRST for all HTML/CSS and clientside JS tasks. Do NOT skip — web APIs evolve rapidly and training weights contain obsolete patterns. Trigger immediately for: - UI/Layout: Modals, dialogs, popovers, Glassmorphism/backdrop-filters, anchor positioning, container queries, `:has()`, `:user-valid`. - Scroll/Motion: View Transitions, Scroll-driven animations, scroll parallax/reveals. - Performance: CWV (LCP, INP), content-visibility, Fetch Priority, image optimization. - System/APIs: Local filesystem access, WebUSB, WebSockets sync, WebAssembly widgets. - Frameworks: Adapting layout/styles in React, Vue, Angular. - General Frontend: Forms, autofill, advanced inputs, custom scrollbars, modern component states, etc. DO NOT trigger for: - Backend: Database SQL, ORMs, Express API routes. - Pipelines: CI/CD deployment, Docker, Actions. - Generic: Local scripts (Python/Go tools), ESLint, Git.

— the description by Google Chrome

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured way to access up-to-date web development patterns, ensuring that implementations follow modern standards rather than relying on potentially outdated training data. It covers a wide range of frontend topics including UI components, performance optimization, browser APIs, and form handling. By integrating this tool, developers can search for specific use cases and retrieve detailed, framework-agnostic guides that include browser support and fallback recommendations.

What it does

Searches for standardized web development patterns and best practices.
Retrieves detailed implementation guides for specific frontend use cases.
Provides guidance on browser compatibility and necessary fallbacks.
Helps avoid ad-hoc solutions and unnecessary dependency bloat.
Supports modern web features like container queries, view transitions, and performance APIs.

When to use it

At the beginning of any frontend feature implementation.
Before creating new components to check for existing standardized patterns.
When evaluating the browser support requirements for modern web features.
When needing to implement performance optimizations like LCP or content-visibility.

Advantages

Ensures use of current, recommended web development practices.
Reduces technical debt by discouraging ad-hoc implementations.
Provides clear guidance on handling browser compatibility and fallbacks.
Promotes the use of native browser capabilities over heavy external dependencies.

Usage examples

“I need to implement a modal using modern web standards. What is the best approach?”: The agent searches for modal-related guides and retrieves the recommended implementation pattern, including any necessary browser fallbacks.
“How can I optimize the loading priority of my LCP images?”: The agent searches for image optimization guides and retrieves the specific instructions for using fetch priority to improve performance.

Install

Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/jetbrains/modern-web-guidance/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip modern-web-guidance.zip -d .agents/skills

Documentation by Google Chrome

Modern Web Guidance

A skill to search for specific web development use cases and retrieve their corresponding best practice guides.

When to use

Must use this skill:

At the start of implementing any web feature.
Before creating a new component, to check if a standardized pattern already exists.
To avoid implementing ad-hoc solutions or loading large dependencies unnecessarily.

Usage Instructions

Step 1. Search Use Cases

Search with an action-oriented query summarizing what you want to achieve using the search command. Run modern-web-guidance directly with npx.

npx -y modern-web-guidance@latest search "<query>" --skill-version 2026_05_16-c5e7870

Example Output:

[
  {
    "id": "optimize-image-priority",
    "description": "Optimize the loading priority of Largest Contentful Paint (LCP) candidate images.",
    "category": "performance",
    "featuresUsed": [ "Fetch priority" ],
    "tokenCount": 985,
    "similarity": 0.7289
  },
  {
    "id": "defer-rendering-heavy-content",
    "description": "Reduce rendering times in content-heavy web pages by deferring rendering for offscreen content.",
    "category": "performance",
    "featuresUsed": [ "content-visibility", "hidden=\"until-found\"" ],
    "tokenCount": 1250,
    "similarity": 0.6961
  }
]

Note: If search results are vague, return no matches, or show low similarity scores, run the list command to browse all guides:
npx -y modern-web-guidance@latest list

Step 2. Retrieve Best Practices

Once you have a relevant id from the search results, call this script using the retrieve command to get the full guide. You can pass multiple IDs separated by commas.

npx -y modern-web-guidance@latest retrieve "<id>"

Example Output: The markdown content of the guide describing implementation steps...

Using npx

IMPORTANT: on Windows, using npx may fail. Use npx.cmd ... instead.
Network access is required for fetching npm packages needed by the task.
If the npx -y modern-web-guidance… command hangs, you may be offline. Try running again in offline mode: npx --offline ….
The --skill-version flag is used to determine if this SKILL.md is out of date. If it is, a warning message is logged to stderr.

Guidelines

Always search first to find the most relevant guides.
These guides are usually framework-agnostic; adapt them correctly to your setup.
Do not hallucinate guides or ignore them; they represent the preferred local standard for the user's project.

Interpreting Browser Support & Fallbacks

Default Behavior: All guides assume Baseline Widely available features are safe to use without fallbacks. For features that are not Baseline widely available, you MUST follow the fallback recommendations in the guide, unless the user has specified a custom browser support policy.
Custom Policies: If the user has already defined explicit browser support requirements, use the browser compatibility data in the guide to determine if a fallback can be safely ignored.
- For Baseline YYYY targets, a feature satisfies this target if its "Baseline since" date is <= YYYY.
- Policy Examples:
  - "Do not implement feature fallbacks." (for exploratory prototypes of the cutting-edge web)
  - "Safari 17.4+" (for internal tools targeting macOS or Tauri-based desktop apps)
  - "Never recommend or implement polyfills; if a Baseline Newly Available feature is required for core functionality, provide a lightweight custom fallback or redesign the approach." (to minimize bundle size and avoid technical debt)
  - "Assume a modern execution environment where Baseline Newly Available features can be used natively, provided they are strictly feature-detected and degrade gracefully." (for progressive enhancement strategies)
Reactive Policy Discovery: Watch for environmental cues to suggest documenting a policy in CLAUDE.md or AGENTS.md. Suggest this if the developer:
- Mentions building for a restricted runtime (e.g., Electron or Tauri).
- Explicitly excludes specific targets (e.g., "we don't support Desktop Chrome").
- Expresses hesitation about polyfill complexity, bundle size, or performance cost.
- Questions if a feature is safe to use without fallbacks.
No defined policy format. This is an example: **Browser Support:** Allow Newly Available features, but only adopt custom fallback code that adds <= 20 lines and does not require external dependencies.

Files

ATTRIBUTION.mdAdded by AutoGineer939 B
LICENSE11.1 KiB
SKILL.md5.7 KiB
guides/accessibility/accessibility.md24.0 KiB
guides/accessibility/accessible-error-announcement.md6.9 KiB
guides/built-in-ai/language-detection.md3.5 KiB
guides/built-in-ai/language-model.md7.1 KiB
guides/built-in-ai/summarizer.md5.9 KiB
guides/built-in-ai/translator.md5.3 KiB
guides/css-layout/css-layout.md19.5 KiB
guides/css/css.md27.0 KiB
guides/css/highlight-text-ranges.md5.4 KiB
guides/forms/animated-select-picker.md7.8 KiB
guides/forms/autofill-address-form.md4.1 KiB
guides/forms/autofill-highlight-inputs.md2.3 KiB
guides/forms/autofill-payment-form.md8.5 KiB
guides/forms/autofill-sign-in-form.md9.9 KiB
guides/forms/autofill-sign-up-form.md11.0 KiB
guides/forms/brand-consistent-forms.md8.3 KiB
guides/forms/branded-select-styling.md5.5 KiB
guides/forms/custom-select-picker-layouts.md5.0 KiB
guides/forms/form-fields-automatically-fit-contents.md5.8 KiB
guides/forms/forms.md13.8 KiB
guides/forms/required-field-feedback.md6.8 KiB
guides/forms/rich-media-picker.md6.6 KiB
guides/forms/select-menu-interaction.md5.6 KiB
guides/forms/validate-input-after-interaction.md8.6 KiB
guides/html/html.md17.5 KiB
guides/passkeys/passkey-authentication.md9.7 KiB
guides/passkeys/passkey-conditional-create.md6.5 KiB
guides/passkeys/passkey-management.md9.3 KiB
guides/passkeys/passkey-reauthentication.md4.9 KiB
guides/passkeys/passkey-registration.md9.3 KiB
guides/passkeys/passkeys.md4.2 KiB
guides/performance/batch-analytics-events.md6.4 KiB
guides/performance/break-up-long-tasks.md2.1 KiB
guides/performance/calculate-total-foreground-time.md2.9 KiB
guides/performance/conditional-async-dependencies.md3.6 KiB
guides/performance/defer-rendering-heavy-content.md6.3 KiB
guides/performance/defer-work-until-scroll-ends.md3.3 KiB
guides/performance/deprioritize-background-fetches.md1.8 KiB
guides/performance/detect-initial-visibility-state.md4.5 KiB
guides/performance/efficient-background-processing.md5.0 KiB
guides/performance/faster-spa-view-transitions.md3.4 KiB
guides/performance/full-session-analytics.md5.7 KiB
guides/performance/identify-heavy-scripts.md4.2 KiB
guides/performance/identify-inp-causes.md5.4 KiB
guides/performance/improve-next-page-load-performance.md7.1 KiB
guides/performance/interactions-in-complex-layouts.md3.4 KiB
guides/performance/optimize-image-priority.md4.0 KiB
guides/performance/optimize-preload-priority.md3.3 KiB
guides/performance/optimize-script-priority.md2.6 KiB
guides/performance/performance.md17.9 KiB
guides/performance/resolution-optimized-pseudo-elements.md2.3 KiB
guides/performance/schedule-tasks-by-priority.md2.2 KiB
guides/performance/sequence-distributed-events.md3.5 KiB
guides/privacy/privacy.md11.0 KiB
guides/security/security.md25.2 KiB
guides/user-experience/adapt-scrollbar-to-contrast-preferences.md3.5 KiB
guides/user-experience/anchor-positioning-tab-underline.md2.9 KiB
guides/user-experience/animate-element-entry-exit.md5.0 KiB
guides/user-experience/animate-to-from-top-layer.md5.5 KiB
guides/user-experience/animate-to-intrinsic-sizes.md5.3 KiB
guides/user-experience/apply-webgl-shaders.md9.9 KiB
guides/user-experience/calculate-event-differentials.md4.4 KiB
guides/user-experience/calculate-with-intrinsic-sizes.md9.6 KiB
guides/user-experience/capture-location-agnostic-data.md3.6 KiB
guides/user-experience/carousel-slide-effects.md8.1 KiB
guides/user-experience/carousel-snap-highlights.md5.7 KiB
guides/user-experience/child-state-based-styling.md4.8 KiB
guides/user-experience/complex-shapes.md3.5 KiB
guides/user-experience/component-specific-light-dark-theme.md9.3 KiB
guides/user-experience/consistent-cross-document-transitions.md11.8 KiB
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guides/user-experience/coordinate-global-events.md3.5 KiB
guides/user-experience/cross-document-transitions.md4.4 KiB
guides/user-experience/customize-scrollbar-color-and-thickness.md2.4 KiB
guides/user-experience/dark-mode.md15.2 KiB
guides/user-experience/declarative-button-actions.md5.4 KiB
guides/user-experience/declarative-dialog-popover-control.md9.2 KiB
guides/user-experience/deliver-optimized-decorative-images.md2.8 KiB
guides/user-experience/design-token-reactivity.md5.7 KiB
guides/user-experience/directional-navigation-transitions.md4.9 KiB
guides/user-experience/dynamic-sibling-animations.md2.6 KiB
guides/user-experience/dynamic-sibling-styling.md3.6 KiB
guides/user-experience/export-html-media-from-canvas.md11.2 KiB
guides/user-experience/expose-canvas-content-to-browser-features.md14.1 KiB
guides/user-experience/flicker-free-client-side-ab-testing.md8.5 KiB
guides/user-experience/fluid-scaling.md3.0 KiB
guides/user-experience/format-human-readable-durations.md4.2 KiB
guides/user-experience/group-element-transitions.md5.0 KiB
guides/user-experience/improve-text-layout-and-legibility.md5.1 KiB
guides/user-experience/individual-transform-properties.md3.6 KiB
guides/user-experience/interactive-content-in-3d-scenes.md13.3 KiB
guides/user-experience/interactive-content-reveal.md5.1 KiB
guides/user-experience/interest-triggered-action-previews.md4.1 KiB
guides/user-experience/interest-triggered-tooltips.md6.8 KiB
guides/user-experience/light-dismiss-a-dialog.md3.6 KiB
guides/user-experience/manage-recurring-intervals.md3.3 KiB
guides/user-experience/model-partial-time-concepts.md4.2 KiB
guides/user-experience/move-dom-element-without-losing-state.md2.5 KiB
guides/user-experience/navigation-drawer.md15.7 KiB
guides/user-experience/overflow-clipping-control.md8.0 KiB
guides/user-experience/parallax-scroll-effects.md8.8 KiB
guides/user-experience/persistent-app-tours.md3.9 KiB
guides/user-experience/persistent-toast-notifications.md1.8 KiB
guides/user-experience/persistent-top-layer-ui.md2.2 KiB
guides/user-experience/physics-based-easing.md5.8 KiB
guides/user-experience/platform-controls-dismiss-dialog.md2.6 KiB
guides/user-experience/position-aware-tooltips.md5.9 KiB
guides/user-experience/precise-text-alignment.md4.7 KiB
guides/user-experience/prevent-text-wrapping.md2.4 KiB
guides/user-experience/pull-to-reveal.md4.7 KiB
guides/user-experience/reduce-style-repetition.md3.9 KiB
guides/user-experience/resilient-context-menus-and-nested-dropdowns.md4.9 KiB
guides/user-experience/same-document-transitions.md8.3 KiB
guides/user-experience/scroll-entry-exit-effects.md7.8 KiB
guides/user-experience/scroll-position-aware-elements.md3.6 KiB
guides/user-experience/scroll-progress-indicator.md6.7 KiB
guides/user-experience/scroll-snap-realtime-feedback.md6.7 KiB
guides/user-experience/scroll-snap-state-sync.md3.9 KiB
guides/user-experience/scroll-target-on-load.md3.3 KiB
guides/user-experience/scrollability-affordance-hints.md3.6 KiB
guides/user-experience/scrollytelling.md8.3 KiB
guides/user-experience/search-hidden-content.md6.7 KiB
guides/user-experience/shaped-cutouts.md7.0 KiB
guides/user-experience/shrinking-header-on-scroll.md6.3 KiB
guides/user-experience/size-aware-styling.md2.9 KiB
guides/user-experience/soft-edge-content-fade.md2.6 KiB
guides/user-experience/stabilize-reactive-state.md3.5 KiB
guides/user-experience/stack-drill-down.md32.9 KiB
guides/user-experience/style-parent-with-has.md6.0 KiB
guides/user-experience/support-global-calendar-systems.md5.7 KiB
guides/user-experience/swipe-to-remove.md26.2 KiB
guides/user-experience/visually-stable-font-fallbacks.md2.9 KiB
guides/user-experience/visually-stable-mixed-fonts.md2.8 KiB
guides/user-experience/visually-texture-content.md3.7 KiB
guides/webmcp/agentic-forms.md5.0 KiB
guides/webmcp/agentic-javascript-tools.md4.1 KiB
guides/webmcp/webmcp.md3.7 KiB

guides/performance/detect-initial-visibility-state.md

Determining if a page was initially loaded in the background (e.g., opened in a new background tab) is critical for accurate performance monitoring. Pages loaded in the background often have delayed rendering and longer metric times (like First Contentful Paint). Identifying these pages allows you to filter them out of performance analytics to avoid skewed data.

The most accurate way to measure this is by using the VisibilityStateEntry API, which reliably records visibility changes on the browser's performance timeline, regardless of when your script actually executes.

Detecting initial visibility and background time

MANDATORY: Use performance.getEntriesByType('visibility-state') to access the exact visibility history. Do not rely solely on checking document.visibilityState at execution time, as it is susceptible to race conditions.

/**
 * Accurately determines visibility state history using the Performance API.
 */
function getVisibilityInfo() {
  // Retrieve VisibilityStateEntry members:
  const entries = performance.getEntriesByType('visibility-state');
  
  if (entries.length > 0) {
    const firstEntry = entries[0];
    
    // If the first performance entry for visibility is 'hidden',
    // the page was loaded in the background.
    const initiallyBackgrounded = firstEntry.name === 'hidden';
    
    // Find the precise, high-resolution timestamp of when the page 
    // was first backgrounded.
    let timeBackgrounded = null;
    for (const entry of entries) {
      if (entry.name === 'hidden') {
        // entry.startTime is used because it provides the exact browser 
        // timestamp of the visibility change, which is required for precision
        timeBackgrounded = entry.startTime;
        break;
      }
    }

    return {
      initiallyBackgrounded,
      timeBackgrounded
    };
  }
}

Fallback strategies

Page visibility state has limited availability. Supported by: Chrome 115 (Jul 2023) and Edge 115 (Jul 2023). Unsupported in: Firefox and Safari.

For unsupported environments, you may fall back to checking the document.visibilityState property or listening for the visibilitychange event.

MANDATORY: You must understand that this fallback approach is often highly inaccurate for determining initial background state. Because scripts can load and execute asynchronously, a page could be opened in a background tab and then foregrounded by the user before your script has finished downloading and executing. When your script finally runs, document.visibilityState will synchronously read as 'visible', and you will incorrectly assume the page was loaded in the foreground, completely missing its initial hidden state. Furthermore, the fallback timestamp lacks the internal precision of the Performance API. If precision is a high priority, do not use the fallback.

/**
 * Fallback implementation using document.visibilityState.
 * This approach is prone to race conditions if the script loads asynchronously.
 */
function getFallbackVisibilityInfo() {
  // Check the state exactly when this script executes.
  // This will fail to detect an initial background state if the user 
  // foregrounded the page before this script executed.
  let initiallyBackgrounded = document.visibilityState === 'hidden';
  
  // If it's hidden now, we approximate that it was hidden from load (time 0).
  let timeBackgrounded = initiallyBackgrounded ? 0 : null;

  // Listen for future visibility changes to capture if it is backgrounded later.
  document.addEventListener('visibilitychange', () => {
    if (document.visibilityState === 'hidden' && timeBackgrounded === null) {
      // performance.now() is used here as a fallback, but it only gives 
      // us the time the event listener fired, not the precise internal 
      // browser time the visibility actually changed.
      timeBackgrounded = performance.now();
    }
  });

  return {
    get initiallyBackgrounded() { return initiallyBackgrounded; },
    get timeBackgrounded() { return timeBackgrounded; }
  };
}

// Modern implementation using VisibilityStateEntry API.
function getVisibilityInfo() {
  // Code omitted here would be the same modern
  // implementation shown earlier in this guide
  // ...
}

// DO: Detect if the VisibilityStateEntry API is available
if ('VisibilityStateEntry' in window) {
  // DO: If VisibilityStateEntry is available, use it first:
  getVisibilityInfo();
} else {
  // DO: If VisibilityStateEntry is unavailable, fall back to `document.visibilityState`:
  getFallbackVisibilityInfo();
}

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

Security

What our scanner noticed· Low risk

Instructions that use the network

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by

Google Chrome

Publisher

JetBrains (Official)

Distributed by

JetBrains

Source

JetBrains/skills · modern-web-guidance · commit 3f53782

Licence

Apache License 2.0 (redistribution allowed)

ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-08

AutoGineer is not affiliated with or endorsed by Google Chrome or JetBrains.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download modern-web-guidance.zip

From the author

AutoGineer summary

What it does

When to use it

Advantages

Usage examples

Install

Documentation by Google Chrome

Modern Web Guidance

When to use

Usage Instructions

Step 1. Search Use Cases

Step 2. Retrieve Best Practices

Using npx

Guidelines

Interpreting Browser Support & Fallbacks

Files

guides/performance/detect-initial-visibility-state.md

Detecting initial visibility and background time

Fallback strategies

Requirements and compatibility

Security

Attribution and licence

Related skills

Web Artifacts Builder

Frontend UI Engineering

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Pick UI Library

Animate Expo

Prototype

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