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web development patterns, ensuring that implementations follow modern standards rather than relying on potentially outdated training data.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
guides/user-experience/content-based-styling.md5.2 KiB
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/user-experience/manage-recurring-intervals.md

Managing Recurring Intervals with Temporal

Calculating recurring intervals, such as subscription billing cycles or payroll periods, has historically been error-prone with the legacy Date object. Adding a month to a date like January 31st is ambiguous (should it be February 28th/29th or March 3rd?).

The Temporal API provides a clean solution with Temporal.PlainDate and its .add() method, which handles month-end transitions predictably using configurable overflow strategies.

How to Implement

MANDATORY: Parse the starting date: Use Temporal.PlainDate.from() to create a date object.
MANDATORY: Add the duration: Use the .add() method with a duration object (e.g., { months: 1 }).
OPTIONAL: Specify overflow behavior: Use the overflow option to control how invalid dates (like Feb 31) are handled.
- 'constrain' (default): Clamps to the last valid day of the month.
- 'reject': Throws a RangeError.

Example: Subscription Billing Cycle

// 1. Parse the start date (e.g., billing starts on Jan 31st)
const startDate = Temporal.PlainDate.from('2024-01-31');

// 2. Add 1 month with default 'constrain' overflow
// Jan 31 + 1 month -> Feb 29 (2024 is a leap year)
const nextBillingDate = startDate.add({ months: 1 });
console.log(`Next billing: ${nextBillingDate.toString()}`); // 2024-02-29

// 3. Add 1 month to Feb 29
// Feb 29 + 1 month -> Mar 29
// Note: Day is preserved if valid, otherwise constrained.
const thirdBillingDate = nextBillingDate.add({ months: 1 });
console.log(`Third billing: ${thirdBillingDate.toString()}`); // 2024-03-29

// Example with 'reject' strategy
try {
  // Jan 31 + 1 month with 'reject' throws because Feb 31 is invalid
  const invalidDate = startDate.add({ months: 1 }, { overflow: 'reject' });
} catch (e) {
  console.log("Caught expected error:", e.name); // RangeError
}

Strategic Implementation & Best Practices

DO use Temporal.PlainDate for calculations that do not depend on specific times or time zones (like calendar dates or billing cycles).
DO understand the default constrain behavior. It is usually what users expect for billing (e.g., Jan 31 -> Feb 28/29 -> Mar 28/29).
DO NOT modify instances directly; Temporal objects are immutable. Operations return a new instance.
DO use overflow: 'reject' if you need to enforce that the resulting date must exist in the calendar and handle failures explicitly.

Fallback strategies

Temporal has limited availability. Supported by: Chrome 144 (Jan 2026), Edge 144 (Jan 2026), and Firefox 139 (May 2025). Unsupported in: Safari.

For browsers that do not yet support the native Temporal API, use feature detection and a polyfill. The standard reference polyfill is @js-temporal/polyfill.

// Check if Temporal is supported natively
(async () => {
  if (typeof Temporal === 'undefined') {
    // Load the polyfill conditionally
    const module = await import("https://esm.sh/@js-temporal/polyfill");
    globalThis.Temporal = module.Temporal;
    // Extend Date.prototype if needed
    Date.prototype.toTemporalInstant = module.toTemporalInstant;
    initializeApp();
  }
})();

function initializeApp() {
  const date = Temporal.PlainDate.from('2024-01-31');
  console.log(date.add({ months: 1 }).toString());
}

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/user-experience/manage-recurring-intervals.md

Managing Recurring Intervals with Temporal

How to Implement

Example: Subscription Billing Cycle

Strategic Implementation & Best Practices

Fallback strategies

Requirements and compatibility

Security

Attribution and licence

Related skills

Web Artifacts Builder

Frontend UI Engineering

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Animate Expo

Prototype

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