Registration

The endpoint resolves the component id in the token through the component registry (service('componentRegistry')). Ids are lowercase (a-z0-9_.:-, at most 100 characters); class names never leave the server.

Where	Id	How
Page	<panel>:<page slug>:<kind>	the page implements Anvil\Page\HasComponents and returns the component from component(string $kind), null for unknown kinds
Resource detail page	<panel>:<resource slug>:<kind>	Resource::detailComponents(), see Components on the detail page
Anywhere else	any id	service('componentRegistry')->register('projects.title', static fn () => new ProjectTitle())

• Page and resource components are found without registration: the registry asks the panels for ids of the form <panel>:<slug>:<kind>.
• The registry lives for one request. Components registered with register() must be registered on every request, not only while the page is rendered; see Making it reachable. Registering an id twice throws a LogicException.
• component() of a page receives only the kind. One page can provide several components (Anvil\Access\ProfilePage has password and mfa).

Permissions of page components

Components of a page need the permission of the page (<panel>.page.<slug>) as well: without it the endpoint answers 404, also for a token issued before the permission was revoked. Every action still needs its own permission on top, usually the permission of the data (tickets.update).

Registering in Events.php

Components that are not part of a page or resource, e.g. a widget used on several pages, are registered in an event that runs on every request:

app/Config/Events.php

use App\Components\ProjectTitle;
use CodeIgniter\Events\Events;

Events::on('post_controller_constructor', static function (): void {
    service('componentRegistry')->register('admin:projects.title', static fn () => new ProjectTitle());
});

Start the id with the panel (admin:) when the component belongs to one panel; the token binds it to that panel anyway, and the test helper dispatchComponent() expects the prefix.

Which way to choose

Situation	Registration
a page of your own with interactive parts	HasComponents on the page
a section on the detail page of a record	Resource::detailComponents()
a row, record or bulk operation	no component: an action
one component used on several pages	componentRegistry()->register()