diff --git a/docs/tutorials/05-notifications.md b/docs/tutorials/05-notifications.md
index fe79dbf3ab..4b0cbb9279 100644
--- a/docs/tutorials/05-notifications.md
+++ b/docs/tutorials/05-notifications.md
@@ -22,7 +22,13 @@ To get a notification an attendee has to:
 
 General notifications are sent to everyone (authenticated and anonymous) who has enabled "General notifications". These are sent manually by conference organizers.
 
-To send a "General notification":
+To send a "General notification" from the command line:
+
+    FIRESTORE_TARGET=production ./hb notify --title "Doors open" --body "Registration is in the main hall." --path /schedule
+
+`--path` is the page the notification opens, or a full `https://` link. `--icon` replaces the icon from `config/notifications`. It asks before sending from production, and `--yes` sends without asking. Without `FIRESTORE_TARGET=production`, it adds the notification to the emulator, where `npm start` runs the function. It needs the `notifications` and `functions` features, since the `sendGeneralNotification` function sends it.
+
+To send one from the Firebase console instead:
 
 1. Got to the [project's Firestore page](https://console.firebase.google.com/u/0/project/_/firestore/data/)
 1. "Start collection" with the ID `notifications`
diff --git a/packages/cli/src/commands/notify.test.ts b/packages/cli/src/commands/notify.test.ts
new file mode 100644
index 0000000000..4091bbdc35
--- /dev/null
+++ b/packages/cli/src/commands/notify.test.ts
@@ -0,0 +1,97 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { confirm } from '../lib/prompt.js';
+import { siteFeatures } from '../utils/site-features.js';
+import { runNotify } from './notify.js';
+
+const { create, doc, collection } = vi.hoisted(() => {
+  const create = vi.fn();
+  const doc = vi.fn(() => ({ create }));
+  const collection = vi.fn(() => ({ doc }));
+  return { create, doc, collection };
+});
+
+vi.mock('../lib/firestore.js', () => ({ firestore: { collection } }));
+vi.mock('../lib/prompt.js', () => ({ confirm: vi.fn() }));
+vi.mock('../utils/site-features.js', () => ({ siteFeatures: vi.fn() }));
+vi.mock('../utils/firebase-project.js', () => ({ resolveFirebaseProjectId: () => 'fest-2027' }));
+
+const output = () => vi.mocked(console.log).mock.calls.map(([line]) => String(line));
+
+describe('runNotify', () => {
+  const isTTY = process.stdin.isTTY;
+
+  beforeEach(() => {
+    vi.spyOn(console, 'log').mockImplementation(() => undefined);
+    vi.mocked(siteFeatures).mockReturnValue({});
+    vi.setSystemTime(new Date('2027-10-15T09:00:00Z'));
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.clearAllMocks();
+    vi.useRealTimers();
+    delete process.env['FIRESTORE_TARGET'];
+    process.stdin.isTTY = isTTY;
+  });
+
+  it('adds the notification to the emulator, which the function sends', async () => {
+    expect(await runNotify({ title: ' Doors open ', body: 'Welcome!', path: '/schedule' })).toBe(
+      true,
+    );
+
+    expect(collection).toHaveBeenCalledWith('notifications');
+    expect(doc).toHaveBeenCalledWith(String(Date.parse('2027-10-15T09:00:00Z')));
+    expect(create).toHaveBeenCalledWith({
+      title: 'Doors open',
+      body: 'Welcome!',
+      path: '/schedule',
+    });
+    expect(output().at(-1)).toContain('to the emulator');
+    expect(confirm).not.toHaveBeenCalled();
+  });
+
+  it('refuses an empty title or body, and a link that could run code', async () => {
+    expect(await runNotify({ title: ' ', body: 'Welcome!' })).toBe(false);
+    expect(
+      await runNotify({ title: 'Doors open', body: 'Welcome!', path: 'javascript:alert(1)' }),
+    ).toBe(false);
+
+    expect(create).not.toHaveBeenCalled();
+    expect(output()).toContain('✘ The title is empty.');
+    expect(output().some((line) => line.includes('path'))).toBe(true);
+  });
+
+  it('refuses when notifications or functions are off, since nothing would send it', async () => {
+    vi.mocked(siteFeatures).mockReturnValue({ functions: false });
+
+    expect(await runNotify({ title: 'Doors open', body: 'Welcome!' })).toBe(false);
+    expect(create).not.toHaveBeenCalled();
+    expect(output()).toEqual(['✘ Nothing would send it: features.functions off.']);
+  });
+
+  it('asks before sending from production, and sends nothing when told no', async () => {
+    process.env['FIRESTORE_TARGET'] = 'production';
+    process.stdin.isTTY = true;
+    vi.mocked(confirm).mockResolvedValueOnce(false).mockResolvedValueOnce(true);
+
+    expect(await runNotify({ title: 'Doors open', body: 'Welcome!' })).toBe(false);
+    expect(create).not.toHaveBeenCalled();
+
+    expect(await runNotify({ title: 'Doors open', body: 'Welcome!' })).toBe(true);
+    expect(confirm).toHaveBeenCalledWith(
+      'Send "Doors open" to every subscribed device of fest-2027?',
+    );
+    expect(output().at(-1)).toContain('to fest-2027');
+  });
+
+  it('needs --yes for production without a terminal to ask in', async () => {
+    process.env['FIRESTORE_TARGET'] = 'production';
+    process.stdin.isTTY = false;
+
+    expect(await runNotify({ title: 'Doors open', body: 'Welcome!' })).toBe(false);
+    expect(create).not.toHaveBeenCalled();
+
+    expect(await runNotify({ title: 'Doors open', body: 'Welcome!', yes: true })).toBe(true);
+    expect(confirm).not.toHaveBeenCalled();
+  });
+});
diff --git a/packages/cli/src/commands/notify.ts b/packages/cli/src/commands/notify.ts
new file mode 100644
index 0000000000..b94c5007aa
--- /dev/null
+++ b/packages/cli/src/commands/notify.ts
@@ -0,0 +1,68 @@
+import { documentMessages } from '../lib/content.js';
+import { confirm } from '../lib/prompt.js';
+import { resolveFirebaseProjectId } from '../utils/firebase-project.js';
+import { findRepoRoot } from '../utils/node-version.js';
+import { siteFeatures } from '../utils/site-features.js';
+
+export interface NotifyOptions {
+  title: string;
+  body: string;
+  /** The page or link the notification opens. */
+  path?: string;
+  icon?: string;
+  /** Send to production without asking. */
+  yes?: boolean;
+}
+
+/**
+ * Sends a general notification to every device that turned general notifications on, by adding
+ * it to `notifications`. The `sendGeneralNotification` function sends it from there. Writes to the
+ * emulator unless FIRESTORE_TARGET=production. Returns whether it was added.
+ */
+export const runNotify = async ({ title, body, path, icon, yes = false }: NotifyOptions) => {
+  const repoRoot = findRepoRoot(process.cwd()) ?? process.cwd();
+  const features = siteFeatures(repoRoot);
+  const off = (['notifications', 'functions'] as const).filter((name) => features[name] === false);
+  if (off.length) {
+    console.log(`✘ Nothing would send it: features.${off.join(' and features.')} off.`);
+    return false;
+  }
+
+  const notification = {
+    title: title.trim(),
+    body: body.trim(),
+    ...(path ? { path } : {}),
+    ...(icon ? { icon } : {}),
+  };
+  const id = String(Date.now());
+  const problems = [
+    ...(notification.title ? [] : ['The title is empty.']),
+    ...(notification.body ? [] : ['The body is empty.']),
+    ...documentMessages(`notifications/${id}`, notification),
+  ];
+  if (problems.length) {
+    for (const problem of problems) console.log(`✘ ${problem}`);
+    return false;
+  }
+
+  const projectId =
+    process.env['FIRESTORE_TARGET'] === 'production'
+      ? resolveFirebaseProjectId(repoRoot)
+      : undefined;
+  if (projectId && !yes) {
+    const question = `Send "${notification.title}" to every subscribed device of ${projectId}?`;
+    if (!process.stdin.isTTY) {
+      console.log(`✘ ${question} Run again with --yes to send it without asking.`);
+      return false;
+    }
+    if (!(await confirm(question))) return false;
+  }
+
+  const { firestore } = await import('../lib/firestore.js');
+  await firestore.collection('notifications').doc(id).create(notification);
+  console.log(
+    `✔ Added notifications/${id} to ${projectId ?? 'the emulator'}. ` +
+      'The sendGeneralNotification function sends it to every subscribed device.',
+  );
+  return true;
+};
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index 8bc32362b0..b1a09798af 100755
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -10,6 +10,7 @@ import { runFirestoreCsv } from './commands/firestore-csv.js';
 import { runFirestoreExport } from './commands/firestore-export.js';
 import { runFirestoreInit } from './commands/firestore-init/index.js';
 import { type InitOptions, runInit } from './commands/init/index.js';
+import { type NotifyOptions, runNotify } from './commands/notify.js';
 import { runSetup } from './commands/setup.js';
 import { runSetupGitHub } from './commands/setup-github.js';
 import { type UpgradeOptions, runUpgrade } from './commands/upgrade.js';
@@ -214,4 +215,24 @@ program
     }
   });
 
+program
+  .command('notify')
+  .description(
+    'Send a push notification to every device that turned on general notifications ' +
+      '(targets the local emulator unless FIRESTORE_TARGET=production is set).',
+  )
+  .requiredOption('--title <text>', 'The title.')
+  .requiredOption('--body <text>', 'The text under the title.')
+  .option('--path <path>', 'The page it opens, such as /schedule, or a full https:// link.')
+  .option('--icon <url>', 'An icon instead of the one in config/notifications.')
+  .option('-y, --yes', 'Send it from production without asking.')
+  .action(async (options: NotifyOptions) => {
+    try {
+      process.exitCode = (await runNotify(options)) ? 0 : 1;
+    } catch (error) {
+      console.log(error);
+      process.exitCode = 1;
+    }
+  });
+
 program.parse();