AI SKILL chrome extensions

Chrome Extensions (Manifest V3) API Reference

Faithful, task-routed reference for building and debugging Manifest V3 Chrome/Chromium extensions — the chrome.* APIs, the manifest format, and the core concepts. Manifest V3 only; Manifest V2 appears only as labeled migration context.

When to use this

Use this skill whenever the task involves a browser extension and any of: a manifest.json with "manifest_version": 3; a background service worker, content scripts, popup, options page, side panel, omnibox, or context menus; any chrome.*/browser.* extension API; message passing or native messaging; declaring permissions/host_permissions; an MV2→MV3 migration; or loading an unpacked extension. It fires even when "Chrome extension" is never said.

Do not use when the task is: Firefox/Safari WebExtension specifics or the webextension-polyfill; general web or Node.js development unrelated to extensions; npm package authoring; Puppeteer/Playwright automation of normal web pages (driving an extension in tests is in scope — see the test reference); Chrome DevTools usage as an end user; or the Web Store listing/review/publishing workflow beyond manifest keys. Those belong to another skill or a generic answer.

Task router

Load only the reference the task needs.

If the task is about...	Read
chrome.runtime, events, alarms, idle, power, onInstalled/onStartup	references/api-runtime-lifecycle.md
offscreen documents, gcm/instanceID push, chrome.extension, types/extensionTypes/dom	references/api-runtime-misc.md
injecting scripts/CSS, chrome.scripting.executeScript, dynamic content scripts, userScripts	references/api-scripting-userscripts.md
tabs, tab groups, windows (query/create/update/sendMessage)	references/api-tabs-windows.md
webNavigation, sessions, history, bookmarks, readingList, topSites, processes, search	references/api-navigation-history.md
blocking/redirecting requests, declarativeNetRequest, webRequest, proxy, cookies, dns	references/api-network-filtering.md
chrome.storage areas/quotas, contentSettings, privacy, fontSettings, browsingData	references/api-storage-settings.md
toolbar action/badge, contextMenus, sidePanel, omnibox, notifications, commands shortcuts	references/api-ui-surfaces.md
DevTools panels/inspectedWindow/network, chrome.debugger (CDP)	references/api-devtools-debugger.md
OAuth tokens, chrome.identity, loginState, certificate/platform keys, WebAuthn proxy	references/api-identity-auth.md
capturing tab/screen media, MHTML, audio devices, text-to-speech	references/api-media-capture.md
downloads, managing installed extensions, runtime permission requests	references/api-downloads-management-permissions.md
system info (cpu/display/memory/storage), printing, scanning, accessibility features	references/api-system-hardware.md
enterprise/ChromeOS APIs, file system provider, IME, wallpaper, VPN	references/api-enterprise-chromeos.md
localizing strings, getMessage, default_locale, _locales	references/api-i18n.md
how the components fit together / getting started	references/concepts-architecture.md
service worker lifecycle, why state is lost, alarms vs setTimeout, offscreen	references/concepts-service-workers.md
content-script isolated vs MAIN world, run_at, match patterns	references/concepts-content-scripts.md
sendMessage/onMessage, ports, external messaging, native messaging	references/concepts-messaging.md
which permission/host_permission to declare, activeTab, match-pattern syntax	references/concepts-permissions.md
choosing a storage area, persisting state, cookies, cross-origin isolation	references/concepts-storage-state.md
install/update events, update rollout, setUninstallURL	references/concepts-lifecycle-updates.md
CSP, no remotely hosted code, web_accessible_resources, privacy	references/concepts-security-privacy.md
converting an MV2 extension to MV3	references/concepts-mv2-to-mv3-migration.md
manifest_version/name/version/icons/default_locale and other identity keys	references/manifest-format-core-keys.md
action/background/content_scripts/permissions/CSP/side_panel/oauth2 keys	references/manifest-capability-keys.md
file_handlers/input_components/tts_engine/COEP-COOP/shared_modules/trial_tokens/devtools_page	references/manifest-specialized-keys.md
confirming a permission string exists and is spelled correctly	references/permissions-list.md
accessibility, favicons, localization formats, notifications UI, extending DevTools	references/howto-ui-and-devtools.md
geolocation, screen capture, WebSockets, WebHID, WebUSB, origin trials	references/howto-web-platform.md
OAuth setup, Google Analytics 4, packaging/self-hosting and loading unpacked (not Web Store review/listing)	references/howto-integrate-distribute.md
debugging the worker/popup/content scripts, Jest, Puppeteer, Selenium	references/howto-test-debug.md

Start from references/INDEX.md if the right file is not obvious.

Runtime workflow

1. Load this SKILL.md and use the task-router to pick the reference for the API, concept, or manifest key in play; read only the files you need.
2. Confirm the required permissions and host_permissions for every API used (cross-check against references/permissions-list.md), and that the manifest is MV3-correct ("manifest_version": 3).
3. Apply MV3-correct patterns; if a sample uses an MV2 pattern, flag it and convert it (references/concepts-mv2-to-mv3-migration.md).
4. Report any detail you cannot verify against a reference rather than guessing; never invent an API name, signature, permission string, or manifest key.
5. Before claiming the skill covers an API, confirm it appears in references/topics.json or a reference file (the verifier enforces the full 83-API coverage list).

Gotchas

Recurring failure modes and what to do instead live in the sibling GOTCHA.md.

References

All depth lives in references/ (start at references/INDEX.md; metadata in references/topics.json). Put routing here in SKILL.md; open a reference only when the router points to it. The references are organized by topic, not one file per source.

Official documentation

Includes original content written for this skill. The official documentation is at https://developer.chrome.com/docs/extensions — consult it to verify anything uncertain, conflicting, or version-specific.

Verification notes

Ground-truth checks for this package (run from the repository root):

python work/verify_chrome_extensions.py .agents/skills/chrome-extensions
python "$env:DEVROOT\SKILLS\skills\skill-drafting\scripts\validate_skill_package.py" "$env:DEVROOT\SKILLS\skills\chrome-extensions"

work/verify_chrome_extensions.py asserts: every reference is listed in references/INDEX.md and has exactly one references/topics.json entry; every reference has an ## Overview and a ## See also whose references/*.md links resolve; a curated preserve-glossary of verbatim terms appears in the references; and all 83 chrome.* APIs are covered. validate_skill_package.py checks the package structure and that no unresolved placeholder text remains. When extending the skill, re-run both and confirm every API name, signature, permission string, and manifest key still matches the official docs exactly (MV3-correct; MV2 only as labeled migration context).