The manifest

Every extension has a connect.json at its root, validated at load time (unknown keys are rejected). It declares the extension's identity, the surfaces it presents, and the capabilities it requests.

Fields

Field	Required	Type	Notes
`manifestVersion`	✅	`1`	Only `1` today.
`id`	✅	string	Reverse-DNS-ish, e.g. `com.example.hello`. Immutable identity; also the on-disk dir name and the `connect-extension://<id>` origin.
`name`	✅	string	Display name.
`version`	✅	string	Dotted-numeric (`1.2.10`). Updates compare these numerically.
`apiVersion`	✅	string	The `connect.*` API generation you target (`"1"`).
`description`		string	Shown in the manager and store.
`icons`		`{ [size]: path }`	Toolbar / manager icon; the shell picks the size nearest a toolbar slot.
`background`		object	A headless script — see below.
`contentScripts`		array	Static content scripts — see connect.scripting.
`ui`		object	Surfaces: `action`, `sidePanel`, `options`, `newTab`, `historyPage`, `bookmarksPage`, `panels` — see below.
`capabilities`		array	The capabilities you request — see Capabilities & consent.
`commands`		object	Keyboard shortcuts — see connect.commands.
`default_locale`		string	Fallback locale for connect.i18n (needs `_locales/<default_locale>/messages.json`).
`key`		string	Pinned signing key (base64 SPKI/DER) — the update trust anchor. See Packaging & trust.
`updateUrl`		string (http/https)	Where to check for updates. See Packaging & trust.

background

"background": {
  "entry": "background.js",          // required: your background script
  "lifecycle": "suspendable",        // persistent | suspendable | ephemeral
  "substrate": "renderer"            // renderer (default) | worker (first-party only)
}

Lifecycle	Behaviour
`persistent`	Stays resident for the profile's lifetime.
`suspendable`	Starts at boot; after ~30s idle it's told `runtime.onSuspend` and torn down, then woken by a subscribed event (told `runtime.onResume`). There is no event replay — re-establish state on resume/boot.
`ephemeral`	Not started at boot; spun up on a wake event, torn down on idle.

substrate: "worker" runs the background in a worker_threads compute host — far lighter than a renderer, faster to wake, no DOM/window. First-party (root-signed) extensions only: a worker cannot be sandboxed like a renderer, so any other trust level is refused and gets the sandboxed renderer. The worker's connect surface is call/onEvent plus runtime/storage/alarms sugar (no Ports).

ui

"ui": {
  "action":    { "entry": "popup.html", "defaultTitle": "…", "width": 360, "height": 520 },
  "options":   { "entry": "options.html" },
  "sidePanel": { "entry": "panel.html" },
  "panels":    [{ "id": "…", "entry": "…", "title": "…" }]
}

action.entry is optional: omit it for a popup-less button that fires action.onClicked instead.
action.width / height seed the popup (bounded 150–800 × 100–600); resize it live with ui.setPopupSize.

Capabilities & consent — declare what your extension can do.
Surfaces & calling the API — wire the pieces together.

Fields

background

ui

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