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manifest-v3

Build and validate MV3 manifest.json files for Chrome extensions.

1|Updated Dec 4, 2025
Search Tags:#CSP#permissions#manifest.json#MV3#Chrome Extension#service_worker
One-click install
npx skills add https://github.com/francanete/fran-marketplace --skill manifest-v3
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: manifest-v3
Source: https://github.com/francanete/fran-marketplace/tree/main/chrome-extension-expert/skills/manifest-v3
Command: npx skills add https://github.com/francanete/fran-marketplace --skill manifest-v3

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

This skill provides a comprehensive reference and practical guidance for building and validating MV3 manifest.json files for Chrome extensions, reducing errors and onboarding time.

Core Features & Use Cases

  • MV3 structure coverage: manifest.json schema, required and recommended fields, service workers, content scripts, permissions, CSP, icons, and side panel configuration.
  • Audit and update workflows: helps design new manifests, audit existing ones, and update fields consistently across extensions.
  • Use Case: imagine creating a new Chrome extension and needing a reliable manifest blueprint to ensure compatibility with MV3.

Quick Start

Use the manifest-v3 skill to generate a MV3 compliant manifest.json skeleton for a Chrome extension with basic fields and permissions.

Frequently Asked Questions about manifest-v3

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
What is a Manifest V3 manifest.json file for a Chrome extension?▼

A Manifest V3 manifest.json file defines the required structure, permissions, service workers, and content scripts for a Chrome extension. It enforces specific fields like manifest_version, name, and version to ensure security and compatibility compliance.

How do I configure service workers in a Manifest V3 manifest.json?▼

To configure service workers in Manifest V3, use the background service_worker field in your manifest.json. This replaces persistent background pages, requiring proper registration and scope definitions to handle extension events securely.

How do I set up permissions and host_permissions in a Chrome extension manifest?▼

You set up permissions and host_permissions in a Manifest V3 manifest.json by declaring API access patterns. Host_permissions separate host matching from standard API permissions, enforcing stricter security boundaries for network requests.

Does Manifest V3 support content_security_policy and web_accessible_resources?▼

Yes, Manifest V3 supports content_security_policy and web_accessible_resources fields. The CSP is configured as an object with extension_pages, while web_accessible_resources requires an array of objects defining resource matches and extension IDs.

What are the required fields for a valid Manifest V3 Chrome extension?▼

The required fields for a valid Manifest V3 Chrome extension are manifest_version, name, and version. Recommended fields include action, icons, and service_worker to ensure full functionality and proper UI integration.

Why is my Manifest V3 extension failing to load due to side panel configuration?▼

Your Manifest V3 extension fails to load if the side_panel configuration lacks a default_path or references an invalid HTML file. The manifest.json must declare the side panel properly with exact path matching to avoid validation errors.

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